NbChatComponent Overview needs more cleaner docs

[nkmithu]

trafficstars

Issue type

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

• [ x] bug report
• [ ] feature request

Issue description

Current behavior: There are no hints on NbChatComponent Overview regarding some imported files.

Expected behavior: In the NbChatComponent overview, there must be cleaner docs about where the 'ChatShowcaseService' came from.

Steps to reproduce:

Related code:

insert short code snippets here

Other information:

npm, node, OS, Browser

<!--
Node, npm: `node --version` and `npm --version`
OS: Windows (7/8/10). Linux (incl. distribution). macOS (El Capitan? Sierra?)
Browser: Chrome/Safari/Firefox/etc?
-->

Angular, Nebular

<!--
Check your `package-lock.json` or locate a `package.json` in the `node_modules` folder.
-->