Add design guidelines from discourse to Vanilla docs markdown

[aaryanporwal]

Done

Migrated corresponding design guidelines into a new tab besides implementation and accessibility tab.

Source of the docs: https://discourse.ubuntu.com/c/design-system/98

QA

• Open demo
• Review new design guidelines pages added for some components:
  • https://vanilla-framework-4927.demos.haus/docs/patterns/badge/design-guidelines
  • https://vanilla-framework-4927.demos.haus/docs/patterns/buttons/design-guidelines
  • https://vanilla-framework-4927.demos.haus/docs/patterns/chip/design-guidelines
  • https://vanilla-framework-4927.demos.haus/docs/patterns/contextual-menu/design-guidelines
  • https://vanilla-framework-4927.demos.haus/docs/patterns/matrix/design-guidelines
  • https://vanilla-framework-4927.demos.haus/docs/patterns/segmented-control/design-guidelines
  • https://vanilla-framework-4927.demos.haus/docs/patterns/slider/design-guidelines
  • https://vanilla-framework-4927.demos.haus/docs/patterns/switch/design-guidelines

[webteam-app]

Demo starting at https://vanilla-framework-4927.demos.haus

[bartaz]

As discussed on Design System Working Group meeting today, the status of design documentation is currently being discussed and the final shape of it is yet to be defined. Therefore we don't want to publish these docs at this time, as they don't reflect what the spec should look like.

I don't want to be throwing away this piece of work as a whole, because while content may not be final, the code changes to make design guidelines show as a new tab are valid and needed. So I think we can drop the markdown content (and the relevant design guidelines config from the yaml file), but keep any other changes. So the new pages can be easily added once needed.

Updated

[bartaz]

As per discussion in roadmap review meeting, we want to include the existing documentation as is and improve on top of that if needed later.

I'm cleaning up this PR and preparing it for review.

[danielmutis]

We need to figure out how to make images better and consistent in terms of size, but for now this is good enough.

[bartaz]

LGTM.

Thanks @aaryanporwal for the initial work on this, it's good to see it go through finally.

[aaryanporwal]

Thanks for taking it forward @bartaz.