Typescript refactor

[thatzopoulos]

All .js files converted to .ts:

• lib/*.js → src/*.ts
• index.js → src/index.ts
• cli.js → src/cli.ts
• __tests__/.test.js → __tests__/.test.ts
• __tests__/helpers.js → __tests__/helpers.ts

New TypeScript Config Files:

• tsconfig.json, jest.config.js, eslint.config.js, src/types.ts, src/ffmpeg.d.ts, src/sitespeed-throttle.d.ts

package.json changes:

• Added build scripts, changed entry points to dist/, added TypeScript devDependencies

Other:

• All CLI tests now reference dist/src/cli.js instead of cli.js

• Updated CLI Args to use slice (non-mutating) instead of splice (mutating)

• Cleanup test method in src/testRunner.ts is now async and closes the browser instance before removing temp files to prevent Jest open handles

• Resolves Typechecking #104

[sergeychernyshev]

As we are on it, let's rename the lib/ to src/ to match the usual convention and move index.ts and cli.ts there as they are no longer directly executable.

[sergeychernyshev]

My tests fail locally for some reason - not sure why they run in CI ;(

Still looking through the rest of the code - will submit more comments later today.

[sergeychernyshev]

None of these are critical changes, I believe so if you feel like making follow-up tickets for improving types so we can deal with it later, it's fine with me.

[sergeychernyshev]

Good to go!