Fix VectorTileSource in SvelteKit builds

[awesomephant]

The problem was caused by a race condition between VectorTileSource and VectorLayer. For some unknown reason, VectorLayer is mounted first in production builds independent of source order (not in dev), which causes it to break because its source doesn't exist yet.

We fix that by nesting VectorLayer inside VectorSource, which makes the mounting order deterministic (other projects take the same approach):

<VectorTileSource>
  <VectorLayer>
  </VectorLayer>
</VectorTileSource>

This PR:

• Adds a waitForStyleLoaded() method to MapContext to queue source/layers in the correct order
• Updates documentation and stories for VectorTileSource and VectorLayer
• Cleans up some related files in the maplibre directory
• Adds e2e testing for this issue and similar dev/build differences in the future
• Downcases workflow titles for style

fix(maplibre): VectorTileSource/VectorLayer race condition (#349)

Closes #348