Add blogger.com to domain list

It looks like your repo doesn't have the actual sources for 1.12 (are there local changes waiting to be pushed to git?), however, this change should work against 1.12. I did not change the manifest version to prevent merge conflicts, so you will still need to bump it to 1.13.

The element on www.blogger.com and draft.blogger.com is also ID #gbg1, so no special rules are added to content.js to make this work.