Add sliders for QML.

This imports and fixes up the QML Widgets made by @deiflou , and adds them to the text properties docker.

(I jammed the angle and curvewidget into text-align to showcase them for the screenshot)

TODO

• Fix up group box buttons.
• Docs
• Signal compressor. (There's... none)
• Fix up negative values (they are accounted for but it doesn't seem to work somehow)
• Fix locale issue for the parser JS.

Test Plan

• Load up Krita
• Make doc
• Check text properties docker, following properties:
  • Character: Font-Size
  • Character: Font-Size-Adjust
  • Character: Font-Style
  • Character: Letter spacing
  • Character: Word spacing
  • Character: Line height
  • Character: Baseline shift
  • Paragraph: Text Indent
  • Paragraph: Tab Size
  • Paragraph: Text-align (the left/center/right buttons are a group)

See also: %Text Tool in woltherav/krita

Formalities Checklist

• I confirmed this builds.
• I confirmed Krita ran and the relevant functions work.
• I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
• I made sure my commits build individually and have good descriptions as per KDE guidelines.
• I made sure my code conforms to the standards set in the HACKING file.
• I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.
• Does the patch add a user-visible feature? If yes, is there a documentation MR ready for it at Krita Documentation Repository?

Reminder: the reviewer is responsible for merging the patch, this is to ensure at the least two people can build the patch. In case a patch breaks the build, both the author and the reviewer should be contacted to fix the build. If this is not possible, the commits shall be reverted, and a notification with the reasoning and any relevant logs shall be sent to the mailing list, kimageshop@kde.org.