* This PR caused the Sidebar.test.ts file tests to fail because TransformStream is not found.
* TransformStream exists in the Node version I'm testing with (20), but it still isn't found by Jest
* Turns out it is a problem with Jest, and the workaround is the simple package jest-fixed-jsdom, which subclasses JSDOMEnvironment testing environment, placing this and several other dependencies in its global object.
* In package.json
- add jest-fixed-jsdom as a devDependency
* In jest.config.cjs
- change testEnvironment to jest-fixed-jsdom
