Added support for running manual and automated tests written in TS.

[martnpaneq]

Suggested merge commit message (convention)

Other (tests): Support for running manual and automated tests written in TypeScript. Remember that test runners do not validate types as we use esbuild which ignores it. Closes ckeditor/ckeditor5#14170, ckeditor/ckeditor5#14171.

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[psmyrek]

Manual and automated tests in TypeScript work fine 🎉

Remarks:

1. I found that the build directory for manual tests contains .ts files, which are not needed there (they are not imported by .html files):

   

   Would it be possible to not copy TypeScript files?

2. In lib/tasks/runautomatedtests.js there is IGNORE_GLOBS that also should skip TypeScript files.

3. I think that a few sentences in the CKE5 docs (contributing section) about the fact that manual and automated tests can be written now in both JavaScript and TypeScript would be useful.

[martnpaneq]

Manual and automated tests in TypeScript work fine 🎉

Remarks:

1. I found that the build directory for manual tests contains .ts files, which are not needed there (they are not imported by .html files):
   
   Would it be possible to not copy TypeScript files?
2. In lib/tasks/runautomatedtests.js there is IGNORE_GLOBS that also should skip TypeScript files.
3. I think that a few sentences in the CKE5 docs (contributing section) about the fact that manual and automated tests can be written now in both JavaScript and TypeScript would be useful.

@psmyrek

1. Fixed.
2. Good catch. I did not test running all tests and without this change the tests would fail.
3. I added a PR for ckeditor5 with some info about TS support in the testing-environment section. I'm not sure if it's the best place, so if you have a better idea please let me know Added docs for TS support for automated and manual tests. ckeditor5#14285

[psmyrek]

LGTM 🎉

[pomek]

LGTM.

It works as expected, tests are compiled, but we lost type checking due to esbuild. It's fine when prototyping things, tho. I feel that at some point, we will bring back ts-loader behind some flag.