Add groundwork for source map support

[marvinhagemeister]

This PR adds a bit of groundwork for supporting source maps in WMR. There is lots more work to do, but this is a complete enough start ready to be merged and to build upon.

• Fix plugin container not forwarding source maps
• Fix invalid null value in sources array of source maps
• Fix .map files not being served
• Fix options.sourcemap not passed to plugins
• Fix options.sourcemap always being false
• Skip transform in import-assertion plugin when no changes were made.
• Merge source maps in transform step
• Update plugins to return source maps when they transform the code

Fixes #699

[changeset-bot]

🦋 Changeset detected

Latest commit: e093373

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
wmr	Patch

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[github-actions]

Size Change: +1.55 kB (0%)

Total Size: 763 kB

Filename	Size	Change
packages/wmr/wmr.cjs	727 kB	+1.55 kB (0%)

ℹ️ View Unchanged

Filename	Size
examples/demo/dist/about/index.html	713 B
examples/demo/dist/alias-outside/index.html	692 B
examples/demo/dist/assets/Calendar.********.css	702 B
examples/demo/dist/assets/style.********.css	624 B
examples/demo/dist/chunks/alias-outside.********.js	138 B
examples/demo/dist/chunks/class-fields.********.js	212 B
examples/demo/dist/chunks/compat.********.js	15.3 kB
examples/demo/dist/chunks/hoofd.module.********.js	1.46 kB
examples/demo/dist/chunks/index.********.js	267 B
examples/demo/dist/chunks/json.********.js	239 B
examples/demo/dist/chunks/meta-tags.********.js	299 B
examples/demo/dist/chunks/prerender.********.js	293 B
examples/demo/dist/class-fields/index.html	703 B
examples/demo/dist/compat/index.html	1.55 kB
examples/demo/dist/env/index.html	779 B
examples/demo/dist/error/index.html	708 B
examples/demo/dist/files/index.html	741 B
examples/demo/dist/index.********.js	7.65 kB
examples/demo/dist/index.html	767 B
examples/demo/dist/json/index.html	711 B
examples/demo/dist/lazy-and-late/index.html	714 B
examples/demo/dist/meta-tags/index.html	778 B

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[marvinhagemeister]

Currently waiting on Rich-Harris/sourcemap-codec#85 to be merged and released. It's the reason our CI is failing here.

[marvinhagemeister]

Alright, used patch-package to patch sourcemap-codec and es-module-lexer locally to support native ESM in node 12.18 and make our CI green again. Filed upstream PRs for both packages. Once they are merged and released we can easily drop our floating patches without hassle.