Add readonly for React Props interface

[xiaoxiangmoe]

see https://reactjs.org/docs/components-and-props.html#props-are-read-only

[orta]

Yeah, that seems like a good call 👍

[swyxio]

fwiw i think a year ago @ferdaber said that the readonly is going to be applied from the @types/react side - not sure if that actually happened

[ferdaber]

For class components I believe they are already read only.

[xiaoxiangmoe]

For function component, readonly is needed.

What should I do now?

[ferdaber]

this PR is probably fine as-is, the updates on the React typings side can come later.

[orta]

I'm not merging any PRs on this repo (content is frozen in preparation for archiving - see #1313) but when we flip the switch, I'll port over PRs to the v2 site

So for now, you can do nothing

[orta]

These two tutorials now redirect to the typescript pages on the tool's side - so I can't reapply any of this to the v2 site. Thanks for the PR though!