Issue 6633 - migrate remaining strings from adblockpluschrome

This is the first PR for -> https://gitlab.com/eyeo/adblockplus/abpui/adblockplusui/issues/154

With https://gitlab.com/eyeo/adblockplus/abpui/adblockplusui/merge_requests/85 we are only migrating popup.json strings, while current PR is for migrating all the remaining one.

Note: en_US/issue-reporter.json stings are sorted alphabetically after import.

See also -> https://issues.adblockplus.org/ticket/6633#comment:3