feat: support ".ts" modules

[aleclarson]

This compiles ".ts" modules into ".d.ts" modules in-memory and forwards them to Rollup.

This removes the need for intermediate files.

Fixes #31

[Swatinem]

looks good in general.

The problem with createProgram is that it is an ahead-of-time operation, as is evident from the heavily increased runtime of the testsuite.

So in order not to regress performance in that case, it would be nice to:

• prefer .d.ts over .tsx? files inside the resolveId, essentially restoring it to what it was before
• lazily call createProgram inside of load when you hit a .tsx? file

I’m not quite sure though if calling createProgram lazily will pick up all the files / compilerOptions correctly (when you don’t start from the entry-point)

[aleclarson]

lazily call createProgram inside of load when you hit a .tsx? file

Instead, I'm going to only use createProgram when the entry point is a .tsx? file :)

Using a .d.ts entry point means you're only using ambient declarations

Note: If you mix .ts and .d.ts entry points, they will all have ts.createProgram called on them. Just for simplicity's sake in the implementation.

[aleclarson]

The failing tests are now unrelated to this PR.

LGTM 👍

[Swatinem]

The failing tests are now unrelated to this PR.

They are related, since you now return .ts instead of .d.ts from the resolveId hook.

I can take care of this tomorrow when I’m at my work machine.