Incorrect Documentation for auth-install.md

[nabgilby]

Issue type

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

• bug report
• feature request

Issue description

Current behavior:

including the @import and @include statements in themes.scss causes compile errors:
Media query expression must begin with '('
in /src/app/@theme/styles/themes.scss (line 10, column 1)

Expected behavior:

No build errors, documentation is corrected with the more details link fixed.

------------- Details -----------------------------------
auth-install.md
5. Last but not least - install the component styles into your themes.scss (more details):
@import '@nebular/auth/styles/all'; // or @import '@nebular/auth/styles/{theme-name}';

// ...

@include nb-install() {
@include nb-theme-global();
@include nb-auth-global(); // append the install mixin inside of the nb-install
};

---

• more details link is broken
• in the ngx-admin example, the @import and @include statements are included in styles.css not themes.scss, including them in themes.scss as well causes multiple errors.

Angular, Nebular

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

@angular/cli":
"version": "1.7.1",
"@nebular/auth": {
"version": "2.0.0-rc.6",