It's useful context for translators but it generates very spammy diffs whenever
a line is added or removed, changing the comments for hundreds or thousands of
msgids needlessly.
We still have the file names so it's relatively easy to search in file to find
the location of the source string.
(cherry picked from commit dbfe36728e)
The files are directed copied from the version which was merged in `3.x`
together with the translations from Weblate.
For future commits we can do cherry-picks from `3.x` to `master` like usual
for the editor translations.
