proto: add support for indentation and nested lists

[web-padawan]

Description

Fixes #1610

Depends on #9007

• Added CSS for nested lists from Quill core
  • Copied mostly without changing, including not working RTL styles (see below)
• Modified logic for keyboard Tab bindings
  • The original issue from Focusing the toolbar is inconsistent vaadin-rich-text-editor#67 seems no longer reproducible and we need to allow Shift + Tab in lists to handle indentation

TODO:

• Fix RTL styles (right now lists in RTL are broken)
  • There are styles for .ql-direction-rtl but these are related to Quill toolbar 'direction': 'rtl' that we don't use
  • Need to update to use :host([dir='rtl']) instead, also keep in mind the .ql-align-right classes
• Add toolbar buttons for increase / decrease indentation
  • Corrresponding Lumo icons needed
• Add tests for ordered / unordered lists
  • Test that indentation works, preferably using sendKeys(). We can rely on .ql-indent classes in unit tests, maybe can also consider snapshots
  • Test that correct htmlValue is returned: <ol> for ordered and <ul> for bullet lists
• Add visual tests for list indentation

Type of change

• Feature

Note

Styles are using counter-set CSS property supported since Safari 17.2

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud