feat(keyboard): move cursor and delete content in contenteditable

[ph-fritsche]

What:

Support cursor movement and editing contenteditable from collapsed selection range a.k.a. a simple cursor when the movement/edit is outside of an already focused TextNode.

Why:
Closes #806

How:

Calculate the next cursor position as observed in the browser.
Use Range API to manipulate the DOM.

Checklist:

• Tests
• Ready to be merged

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[codecov]

Codecov Report

Merging #822 (c408bcd) into beta (4f56856) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              beta      #822    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           79        80     +1     
  Lines         1578      1679   +101     
  Branches       559       610    +51     
==========================================
+ Hits          1578      1679   +101     

Impacted Files	Coverage Δ
src/keyboard/plugins/arrow.ts	100.00% <100.00%> (ø)
src/utils/edit/prepareInput.ts	100.00% <100.00%> (ø)
src/utils/focus/cursor.ts	100.00% <100.00%> (ø)

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[github-actions]

🎉 This PR is included in version 14.0.0-beta.6 🎉

The release is available on:

• npm package (@beta dist-tag)
• GitHub release

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