feat: Add esquery selector textfield & highlighting of matched code

[pkerschbaum]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

MVP for esquery selector playground (#79): textfield to enter selectors, matching code get's highlighted:

Future ideas:

• add matches count, tooltips for matches, or syntax highlighting of the selector itself like https://regexr.com/
• highlight matching accordions (nodes) in the AST tool

What changes did you make? (Give an overview)

• add reusable component TextField, styled similar to Button
• add textfield for esquery selector between Navbar and Editor+Tool panels
• add switch to JS options to toggle the esquery selector textfield
  • is by default off --> people need to opt-into displaying the esquery selector textfield
• add Codemirror extension + CSS to highlight ranges via its "Decoration" feature
• add highlighted ranges if the esquery toggle is enabled in the JS options, and the esquery selector matches ranges

Related Issues

Fixes #79

Is there anything you'd like reviewers to focus on?

[linux-foundation-easycla]

• ✅login: pkerschbaum / (dadf787)
• ✅login: pkerschbaum / (dadf787, 9483a16)

The committers listed above are authorized under a signed CLA.

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