🐛 BUG: Alpine intellisense does not work in `.astro` files

[bholmesdev]

Describe the Bug

I tried out the Alpine extensions for syntax highlighting and intellisense, and found neither seem to work in .astro files; only .html. It sounds like VS Code has a customData format we need to adhere to according to @Princesseuh.

To quote the README:

This extension aims to keep as small a footprint as possible by injecting a simple grammar to provide JavaScript highlighting rather than implementing an entirely new language and by using the Custom Data Extension to add custom HTML attributes.

Steps to Reproduce

1. Install the Alpine intellisense extension
2. Visit a .html file. Note that typing an example like <p x- pulls up intellisense.
3. Do the same in .astro file. Note intellisense options do not appear.