feat: system level extensions

[rbreeze]

Example extension:

((window) => {
  const component = () => {
    return React.createElement(
      "div",
      { style: { padding: "10px" } },
      "Hello World"
    );
  };
  window.extensionsAPI.registerSidebarExtension(
    component,
    "Test Ext",
    "/hello",
    "fa-flask"
  );
})(window);

Signed-off-by: Remington Breeze remington@breeze.software

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Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR states what changed and the related issues number (used for the release note).
• I've included "Closes [ISSUE #]" or "Fixes [ISSUE #]" in the description to automatically close the associated issue.
• I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• Does this PR require documentation updates?
• I've updated documentation as required by this PR.
• Optional. My organization is added to USERS.md.
• I have signed off all my commits as required by DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My build is green (troubleshooting builds).

[codecov]

Codecov Report

Base: 45.67% // Head: 45.67% // No change to project coverage 👍

Coverage data is based on head (b074bd7) compared to base (76fe1d5).
Patch has no changes to coverable lines.

❗ Current head b074bd7 differs from pull request most recent head 5163d25. Consider uploading reports for the commit 5163d25 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #10758   +/-   ##
=======================================
  Coverage   45.67%   45.67%           
=======================================
  Files         236      236           
  Lines       28699    28699           
=======================================
  Hits        13108    13108           
  Misses      13799    13799           
  Partials     1792     1792           

Impacted Files	Coverage Δ
util/settings/settings.go	51.36% <0.00%> (ø)

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[alexmt]

LGTM. Apparently is fixes #10780 as well