feat(web-workers): Add rollup-plugin-web-worker-loader

[schlusslicht]

What this pull request does
This pull request aims at providing a convenient way to create inlined JavaScript source blobs which contain all dependencies to run within a WebWorker execution context.

What this pull request contains

• implementation (here)
• worker-loader cli option (here)
• TypeScript-enabled test case (here)
• small documentation change/example (here)
• repository to test the implemented feature "in the wild" (here, npm run microbundle)

Further notes
I've tried to adhere to the standards of the codebase and the resulting changes can successfully build the rollup-typescript-webworkers repository, which is an example how to use the rollup-plugin-web-worker-loader. Feel free to point me in the right direction if You consider to merge this, but need some changes to be done! :)

Issues/drawbacks
In order to successfully use the rollup-plugin-web-worker-loader, I had to disable the Rollup build cache when running microbundle with the plugin enabled (see here). This seems to be related to an incompatibility between this plugin and something else. I've tried to investigate further, but dropped the lead after spending to much time digging through the Rollup internals. As for now, the behavior of microbundle/Rollup build cache does not change, when building without this feature.

[changeset-bot]

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[developit]

Thanks for the comprehensive PR. I'm a fan of using workers and making worker usage easier. That said, I'm not sure a prefix is the right direction for Microbundle to take. It's specific to Worker, which means we'd need to add plugins if we ever wanted to provide the identical functionality for worklets, SharedWorker, worker_threads, frames, etc.

A syntax detection-based approach like that of rollup-plugin-off-main-thread or rollup-plugin-worker would get around this concern. Ultimately, I think it might make more sense to land support for the general-purpose import workerURL from 'bundle:./worker.js' import prefix, since that can be easily used to instantiate workers and worklets.

Thoughts?

[schlusslicht]

Thank You for Your review and feedback, Jason! I'm currently engaged in other projects, but will (re)evaluate this PR/funcionality some time in the future. Unless someone is faster 😃. Would like to give You an ETA, but my timeline is too messy currently.

[developit]

This landed in #815 / #867.

[schlusslicht]

Hello! Yeah, I did follow up on these events recently. But as I needed this specific feature/plugin (to bundle workes inline within my library), I went ahead and monkey-patched microbundle before usage within my project ... 🙈

.. sorry that I was of no further assistance when it came to implementing/merging the alternative implementation.