temp esc editor key, update open/close file menu aria label

[raclim]

Changes:

• Switches the aria labels for the Open/Close File menu button to address: "Open/close sketch files navigation has opposite labels. Labelled 'open' when it's open and 'close' when it's closed."
• Adds a temporary key Shift-Metakey-E to escape the keyboard trap in the CodeMirror editor. Will be removed once upgraded to Codemirror 6, which should have Esc-Tab do this as default.

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

[release-com]

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• p5.js-web-editor
  • app-ted6e40.release.editor.p5js.org/
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🔧Environment Status : https://app.release.com/public/Processing%20Foundation/env-16b032b3bb