Document use of Astro’s JSX types

[delucis]

What kind of changes does this PR include?

• New or updated content

Description

• Closes Document using / extending the Astro JSX definitions  #984
• Adds a “Built-in attribute types” subheading to the Typescript page’s “Component Props” section that explains how to use and also extend Astro’s built-in JSX definitions.

@Princesseuh I tried these examples out in the docs repo and it seems to work without the need for the /// directive. Would you mind reading through this and letting me know if you think this covers what you imagined? 💜

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[Princesseuh]

@Princesseuh I tried these examples out in the docs repo and it seems to work without the need for the /// directive.

This is true in Astro files only because the language server inject those types into Astro files in the editor, however it's technically improper code 😄 Additionally, it is needed in other files, so definitely needs to be documented. Our own image integration use it in a .ts file, for instance

[delucis]

@Princesseuh Added a note to that effect: