Focus / Klar v39.0

This is Focus/Klar v39.0 with the following changes:

• https://github.com/mozilla-mobile/focus-ios/milestone/37?closed=1

This major release introduces a light theme and numerous small bug fixes and improvements.

Four improvements were submitted as part of Hacktoberfest:

• https://github.com/mozilla-mobile/focus-ios/pulls?q=is%3Apr+label%3Ahacktoberfest-accepted+is%3Aclosed+milestone%3A%22Focus%2FKlar+v39.0%22

Many thanks to @rizwankce, @kcome, @aaronraimist and @mintbomb27 for these contributions 🥇