This PR adds docs for the methods in the TLShapeUtil class.
I think that it's a good page to have docs on, as it shows people what's
possible with the custom shape API.
Currently, our docs are not showing `@param` info for lots of methods,
including the ones added in this PR.
I'll do fix for that in a follow-up PR, so that it's easier to review.
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Note: Moving forward, we probably want to consider **_where_** these
docs are shown, and how we achieve that.
For example, do we put the docs for these methods in:
* The docs page for the `TLShapeUtil` class?
* The docs pages for the handler types, eg:
[`OnResizeHandler`](http://localhost:3000/gen/editor/OnResizeHandler-type)?
* Both?
Right now, I opted for putting them in the the TLShapeUtil class, as it
keeps them all in one place, and it's what we already do for some
others.
We should consider both - what works best for the docs? and what works
best for code editors?
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This PR also includes a fix to our pre-commit step that @SomeHats did.
