Add JavaScript example for jslib/testing/3-integration-suite/

[ayewo]

In continuation of the work started in #3927, this PR when closed, will add:

• example/jslib/testing/
  • 3-integration-suite/: demonstrating usage of at least 2 Javascript integration testing frameworks cypress and playwright

I've figured out a way to simplify the compilation logic in TypeScriptModule, specifically in:

mill/javascriptlib/src/mill/javascriptlib/TypeScriptModule.scala

Lines 136 to 159 in 7fbad41

	def compilerOptionsBuilder: Task[Map[String, ujson.Value]] = Task.Anon {
	val declarationsOut = Task.dest / "declarations"
	val combinedPaths =
	upstreamPathsBuilder() ++
	generatedSources().map(p => ("@generated/*", p.path.toString)) ++
	modulePaths() ++
	compilerOptionsPaths().toSeq
	val combinedCompilerOptions: Map[String, ujson.Value] = compilerOptions() ++ Map(
	"declarationDir" -> ujson.Str(declarationsOut.toString),
	"typeRoots" -> ujson.Arr(
	(npmInstall().path / "node_modules/@types").toString,
	declarationsOut.toString
	),
	"paths" -> ujson.Obj.from(combinedPaths.map { case (k, v) =>
	val splitValues =
	v.split(":").map(s => s"$s/*") // Split by ":" and append "/*" to each part
	(k, ujson.Arr.from(splitValues))
	})
	)
	combinedCompilerOptions
	}

Still testing to make sure it doesn't introduce any side effects.

[lihaoyi]

@ayewo I see you have these commented out

//  object playwright extends TypeScriptTests with TestModule.Jest
//  object cypress extends TypeScriptTests with TestModule.Vitest

Should they work if uncommented, or is it still WIP?

[ayewo]

@ayewo I see you have these commented out

//  object playwright extends TypeScriptTests with TestModule.Jest
//  object cypress extends TypeScriptTests with TestModule.Vitest

Should they work if uncommented, or is it still WIP?

Still WIP.

[lihaoyi]

closing in favor of #4253