Hot reload is very slow

### Issue type

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

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

### Issue description

**Current behavior:**

ngx-admin is being very slow to rebuild in a hot-reload process. Almost 1 minute with a beast computer with no modifications on the current repo.

**Expected behavior:**

Hot-reloading in a decent amount of time.

**Steps to reproduce:**

```sh
git clone https://github.com/akveo/ngx-admin.git
cd ngx-admin
npm i
npm start
# modify any source file and the hot reload will take approx. 1minute
```

**Related code:**

```
none
```

### Other information:

**npm, node, OS, Browser**
```
Angular CLI: 7.3.7
Node: 11.6.0
OS: win32 x64
Angular: 7.2.11

ngx-admin: v3.2.1
```

**Angular, Nebular**
`latest`