How to setup Social Link authentication

### Issue type

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

* [ ] bug report
* [x] feature request

### Issue description

**Current behavior:**

Example of Social Link authentication is not available.
**Expected behavior:**

Example of Social Link authentication with sample implementation.
**Steps to reproduce:**

NA
**Related code:**

```
insert short code snippets here
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### Other information:

**npm, node, OS, Browser**
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**Angular, Nebular**
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