Dark mode for FAQ component

[kkartunov]

Like shown on https://marvelapp.com/prototype/bj002ag/screen/77662351

[kkartunov]

Test page for QA:
https://community-app.topcoder.com/examples/contentful/viewport/1ekIMzLLz2CrkRxPgA4FZ1

The red section implements the new theme.

[SathyaJayabal]

@kkartunov,
Separators are not 40 % opaque like in design
Text and arrow must be white

[kkartunov]

@SathyaJayabal the QA url is https://test-community-app.topcoder-dev.com/examples/contentful/viewport/1ekIMzLLz2CrkRxPgA4FZ1

You have QAed the prod version which we want to update :)

[SathyaJayabal]

verified on test