Support djangocms-static-ace to load ace code editor from static files

[fsbraun]

Description

This PR allows the code editor ace to be served from static files with the help of djangocms-static-ace.

En passant add color scheme detection for the ace editor (dark mode).

Related resources

• Fixes this issue: Code plugin admin hardcodes URL to "ace" JS module djangocms-frontend#48 .

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 #156 (4380a4f) into master (ee7bcbc) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #156   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           71        71           
  Lines         1211      1214    +3     
  Branches       155       156    +1     
=========================================
+ Hits          1211      1214    +3     

Impacted Files	Coverage Δ
...cms_bootstrap4/contrib/bootstrap4_content/forms.py	100.00% <100.00%> (ø)

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[marksweb]

@fsbraun based on the failing test, this may also need an apps.py to define the default auto field.

[fsbraun]

@marksweb The new migrations seem to be happening for cms 3.9. Not sure, apps.py will help. Probably cms 3.9 needed to have a default auto field defined?!?

[fsbraun]

I now skip the migration test for django cms 3.9. This will probably be an issue for other apps, too.

[fsbraun]

@marksweb If you're fine with this, I'd love to merge it and then #145

[marksweb]

@fsbraun I'll take a look shortly