NbInputModule not found

### Issue type

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

* [x] bug report
* [ ] feature request

### Issue description

**Current behavior:**
When trying to import NbInputModule as described in the [documentation](https://akveo.github.io/nebular/docs/components/input/overview#nbinputdirective) the Module isn't found

**Expected behavior:**
Successful import of NbInputModule to use it for ``

**Steps to reproduce:**
Try to import NbInputModule in app.module.ts in imports: [...]

**Related code:**

There is not really any code to showcase this issue

### Other information:

**npm, node, OS, Browser**
node: v12.6.2
npm: 6.13.1
Os Windows 10
Browser: Chrome

**Angular, Nebular**
Angular: 9.1.0
Nebular: 4.2.2