fix: Modify language menu for pages only if it is present

[fsbraun]

Description

Pages do not need to have language menus (even if USE_I18N is True). Trying to modify a non-existing menu leads to an attribute error.

This PR also runs makemessages and includes updated .mo files.

Finally, the locale path is included in the manifest for future packaging.

Steps to reproduce

• Create a project with a single page
• Try previewing any page

Related resources

• Language menu issue #334
• #...

Checklist

• I have opened this pull request against master
• I have added or modified the tests when changing logic
• I have followed the conventional commits guidelines to add meaningful information into the changelog
• I have read the contribution guidelines and I have joined #workgroup-pr-review on
  Slack to find a “pr review buddy” who is going to review my pull request.

[codecov]

Codecov Report

Merging #333 (f1d6737) into master (91eafe1) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #333   +/-   ##
=======================================
  Coverage   90.93%   90.93%           
=======================================
  Files          72       72           
  Lines        2536     2536           
  Branches      358      358           
=======================================
  Hits         2306     2306           
  Misses        170      170           
  Partials       60       60           

Impacted Files	Coverage Δ
djangocms_versioning/cms_toolbars.py	96.90% <100.00%> (ø)

[marksweb]

I'll install and test this in the morning 👍

[marksweb]

Ok checked this change with page editing and all seems well.