add core help strings to gettext source file

This will allow us to put these up on Weblate and have people start
translating them.  Then we can figure out how to actually include and
deploy the translations later.  It is unfortunately non-trivial, since
we have to manually figure out the install paths.
1 job for localization-template in 23 minutes and 25 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #17756985
test

00:23:25