Plone.app.mosaic

--------------------

- Code cleanup in properties modal.
[petschki]

- Fix moving Tiles when there are `max-columns` tiles within a row.
[petschki]

- Layout column handle drag/drop fixes and cleanup.
[petschki]

--------------------

- Fixed properties modal.
[petschki]

- Update to mockup 5.0.0-alpha.18
[petschki]

--------------------

- Update to mockup 5.0.0-alpha.17 -> This fixes file upload in modal forms.
[petschki]

- Fixed old upgrade step that tried to set plone.lessvariables.
Ignore this on Plone 6, because it fails.
[maurits]

--------------------

- Update to mockup 5.0.0-alpha.12
- Packaging fixes
[petschki]

--------------------

- Refactoring of mosaic editor:

- ES6 class construction
- use mockup `pat-tinymce`
- use mockup `pat-plone-modal`
- get rid of $.mosaic initialization
- start getting rid of jQuery (uncompleted)

[petschki]

- Do not load mosaic editor on babel add form (`++addtranslation++...`).
[jensens]

- pyupgrade, black, isort
[jensens]

- Remove buildout and use mxdev/Makefile based approach.
Plone 6 only.
[jensens]

- Remove obsolete BS3 demo.
[jensens]

- Add row columns presets feature for the row stiles
[balavec]

- Fix advanced mode tile insert
[balavec]

- Update for Bootstrap 5
[agitator]

------------------

- Bugfix: Use TinyMCE `getContent()` to get editor contents on save
[frapell]

- Add ``bootstrapPath`` less variable.
Now the bundle can be built with ``plone-compile-resources``.
Contains an upgrade step.
[thet]

- Fix Flake8 errors
[jugmac00]