CodeSearch: Fix #771

Add overflow-x: scroll
CodeSearch: Remove `[]` from the sourceName.
Gifs: Move map to normalize function.
Gifs: Encode the search query before adding to URL.

Also, use remainder in the handle function.
Merge pull request #818 from duckduckgo/jag/gifs

Gifs: Small modifications to make it ready for release
Merge pull request #812 from duckduckgo/jag/codesearch

:+1: CodeSearch: Fix #771