feat: add page layout, header, panel

[fran-ink]

⚠️ Do not merge this yet, I want a PR branch to test some thing 😄

But basically, adds a couple of layout components to help users have a consistent experience through the apps. I still wanted to keep it very flexible, so the structure is the following:

<InkLayout {...navProps}>
  <InkPageLayout columns={1 | 2 | 3}>
     <InkPanel>Stuff in column one</InkPanel>
     <InkPanel>
          <InkHeader title="Header for Panel 2" />
         <div>Stuff in column two</div>
     </InkPanel>
     ...
  </InkPageLayout>
</InkLayout>

I noticed the layout for the app was the same as the Modal, so this structure also allows us to reuse the Panel and Header components for the Modal.

You can also center the panel with centered: true. What is really nice is if you have one element, it will center it. But if you have two, it will keep the header at the top, but center the second one. I think this makes for a very nice experience.

I know it's like... 3 layers of nested components, but I do prefer the way we can compose a layout with all of them, and it still allows people to inject their own layout, but still reuse the panels.

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