`ng test` not working: "Module not found..."

### Issue type

**I'm submitting a ...** (check one with "x")

* [x] bug report
* [ ] feature request
* [ ] question about the decisions made in the repository

### Issue description

**Current behavior:**

Unit testing with `ng test` fails with error:

```
(base) raschidjfr@MacBook-Pro-de-Raschid ngx-admin % ng test
Warning: Entry point 'ngx-echarts/core' contains deep imports into '/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/echarts/lib/echarts'. This is probably not a problem, but may cause the compilation of entry points to be out of order.
10% building 2/2 modules 0 active20 09 2020 19:43:28.459:WARN [karma]: No captured browser, open http://localhost:9877/
20 09 2020 19:43:28.474:INFO [karma-server]: Karma v5.0.9 server started at http://0.0.0.0:9877/
20 09 2020 19:43:28.474:INFO [launcher]: Launching browsers Chrome with concurrency unlimited
20 09 2020 19:43:28.477:INFO [launcher]: Starting browser Chrome

ERROR in multi ./node_modules/bootstrap/dist/css/bootstrap.css ./node_modules/typeface-exo/index.css ./node_modules/roboto-fontface/css/roboto/roboto-fontface.css ./node_modules/ionicons/scss/ionicons.scss ./node_modules/font-awesome/scss/font-awesome.scss ./node_modules/socicon/css/socicon.css ./node_modules/nebular-icons/scss/nebular-icons.scss ./node_modules/pace-js/templates/pace-theme-flash.tmpl.css ./src/app/@theme/styles/styles.scss
Module not found: Error: Can't resolve '/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss' in '/Users/raschidjfr/Documents/git/github/ngx-admin'
resolve '/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss' in '/Users/raschidjfr/Documents/git/github/ngx-admin'
using description file: /Users/raschidjfr/Documents/git/github/ngx-admin/package.json (relative path: .)
Field 'browser' doesn't contain a valid alias configuration
using description file: /Users/raschidjfr/Documents/git/github/ngx-admin/package.json (relative path: ./node_modules/font-awesome/scss/font-awesome.scss)
no extension
Field 'browser' doesn't contain a valid alias configuration
/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss doesn't exist
.ts
Field 'browser' doesn't contain a valid alias configuration
/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss.ts doesn't exist
.tsx
Field 'browser' doesn't contain a valid alias configuration
/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss.tsx doesn't exist
.mjs
Field 'browser' doesn't contain a valid alias configuration
/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss.mjs doesn't exist
.js
Field 'browser' doesn't contain a valid alias configuration
/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss.js doesn't exist
as directory
/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss doesn't exist
[/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss]
[/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss.ts]
[/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss.tsx]
[/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss.mjs]
[/Users/raschidjfr/Documents/git/github/ngx-admin/node_modules/font-awesome/scss/font-awesome.scss.js]
@ multi ./node_modules/bootstrap/dist/css/bootstrap.css ./node_modules/typeface-exo/index.css ./node_modules/roboto-fontface/css/roboto/roboto-fontface.css ./node_modules/ionicons/scss/ionicons.scss ./node_modules/font-awesome/scss/font-awesome.scss ./node_modules/socicon/css/socicon.css ./node_modules/nebular-icons/scss/nebular-icons.scss ./node_modules/pace-js/templates/pace-theme-flash.tmpl.css ./src/app/@theme/styles/styles.scss styles[4]
20 09 2020 19:43:46.414:INFO [Chrome 85.0.4183.102 (Mac OS 10.15.6)]: Connected on socket ALBB5HsXflPdjty5AAAA with id 29982972
Chrome 85.0.4183.102 (Mac OS 10.15.6): Executed 0 of 0 SUCCESS (0.001 secs / 0 secs)
TOTAL: 0 SUCCESS
TOTAL: 0 SUCCESS
```

**Expected behavior:**

Unit test should build and run

**Steps to reproduce:**

1. clone repo: `$ git clone git@github.com:akveo/ngx-admin.git`
2. instal npm modules: `$ npm i`
3. run tets: `$ ng test`

**Related code:**

The problem seems to be that path to FontAwesome's styles in [angular.json](https://github.com/akveo/ngx-admin/blob/master/angular.json#L130) is outdated:

```js
// angular.json
"architect": {
"test": {
"options": {
"styles": [
"node_modules/font-awesome/scss/font-awesome.scss", // <-- this line
],
...
```

### Other information:

**npm, node, OS, Browser**
Node, npm: `v12.18.2` and `6.14.5`
OS: MacOS 10.15.6 (19G2021)
Browser: Chrome 85.0.4183.102 (Build oficial) (64 bits)

**Angular, Nebular**

```js
// package.json
"dependencies": {
"@akveo/ng2-completer": "^9.0.1",
"@angular/animations": "^9.0.4",
"@angular/cdk": "^9.1.2",
"@angular/common": "^9.0.4",
"@angular/compiler": "^9.0.4",
"@angular/core": "^9.0.4",
"@angular/forms": "^9.0.4",
"@angular/google-maps": "^9.1.0",
"@angular/platform-browser": "^9.0.4",
"@angular/platform-browser-dynamic": "^9.0.4",
"@angular/router": "^9.0.4",
...
"@nebular/auth": "5.0.0",
"@nebular/eva-icons": "5.0.0",
"@nebular/security": "5.0.0",
"@nebular/theme": "5.0.0",
...
}
```