feat: support .mts .cts

[bluelovers]

#1007

#1414

[cspotcode]

Like all PRs, this will need tests before we can merge it.

[bluelovers]

i don't know how make test for this

[cspotcode]

A proper test needs to use the feature that you're adding. So if you're adding support for new file extensions, then the test needs to use the file extensions to prove that ts-node behaves the way you want it to behave.

Most of ts-node's tests are very straightforward. They run the ts-node CLI and tell it to run code in a sample project. The code that spawns the CLI lives in ./src/test/**.spec.ts. The sample project lives in ./tests

Here's an example you can use as a starting point.
https://github.com/TypeStrong/ts-node/blob/main/src/test/index.spec.ts#L580-L584
https://github.com/TypeStrong/ts-node/tree/main/tests/main-realpath

This example tests something about symlinks. Obviously that's not relevant for your test. But the idea is the same: you have a sample project, and it gets invoked.

[cspotcode]

This is gonna need more work:

• must register .js extension handler even if allowJs is off
  • necessary to compile .cjs, .cts, and to throw ESM error for .mts
• consider conditionally registering .mjs extension when moduleType overrides are set
• modify assertScriptCanLoadAsCJSImpl to understand that .mts overrides package.json
• modify ESM loader to resolve from .mjs / .cjs to .mts / .cts, the same way it does for .js/.jsx/.ts/.tsx

And finally...

• test coverage of the above

[cspotcode]

Might want to ship with #1361 so that require("./foo.cjs") resolves to require("./foo.cts")

[cspotcode]

Docs updates to go with this:

Update moduleTypes jsdoc and markdown: they say ts cannot use mts and cts; this is wrong

[cspotcode]

Rolling into #1694