Add Solid to JSX in Getting started

[wooorm]

Initial checklist

• [X] I read the support docs
• [X] I read the contributing guide
• [X] I agree to follow the code of conduct
• [X] I searched issues and couldn’t find anything (or linked relevant results below)

Problem

Solid supports MDX 2 with https://github.com/high1/solid-jsx but it’s not listed in the Getting started section.

Solution

Add a small section here: https://mdxjs.com/docs/getting-started/#jsx. Include some basics and defer to Solid/solid-jsx’ docs

Alternatives

n/a

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@high1 something you might be interested in working on?