Don't start CI builds for the changes to message catalogs only

We currently don't use these files in the existing builds.

It might be a good idea to add another GitHub Action workflow checking
the message catalogs compilation that would be executed _only_ for the
changes to them, but this can/will be done later.

appveyor.yml

@@ -10,6 +10,7 @@ skip_commits:
     - demos/
     - docs/
     - interface/
+    - locale/
     - misc/
     - include/wx/dfb/
     - src/dfb/