Form layout

[pngwn]

Implements form groupings when there is more than 1 adjacent form. Part of #1041.

Run demo/fake_gan_complex to see this in action in a complex flow of components (with multiple foprms groups of different sizes).
Run demo/kitchen_sink to see all forms together.

@gary149 Few implementation notes here. I added a new class to the components layer of tailwind to apply the new spacing. We had to switch to margins instead of gap because you can't switch off gap for certain elements. The lobotomised owl selector is pretty standard for child component spacing though and gives us the flexibility we need. Let me know what you think.

We do have some styling in the global css and some in the components themselves but since those styles are applied to components directly we still remain in complete control, so I think it should be ok.

Screenshots

[abidlabs]

Wowow the screenshots (especially the second one) look so nice!

@pngwn what do you think about a dedicated gr.Section([component1, component2...]) that takes in a list of components for the use case shown in the 2nd screenshot? For 2 reasons:

• Using a standard Markdown component is actually not ideal for users since now the value of that Markdown element gets passed as one of the parameters of the function. (In the case of this mock function, it doesn't matter, but it would matter for real functions)
• We could make sections collapsible, which would lead to really nice UI especially when there are a lot of options (see Implementation of a collapsible accordion (for advanced options for e.g.) #938)

Beyond the scope of this PR, but we can create an issue around it.

[pngwn]

@abidlabs I think it would be good to have a conversation around the narrative for interface + blocks and where those boundaries like. We could say to users that for layouts like this then they should move to blocks. That said I think your proposed 'section' component would be really nice. It could take a title, aribtrary (and optional) markdown and a list of components. It could be collapsible, configurable via a flag.