Proposal for observability overview page

[pipo02mix]

What this PR does / why we need it

Towards https://github.com/giantswarm/giantswarm/issues/30734

Things to check/remember before submitting

• If you made content changes

  • Run make dev to render and proofread content changes locally.
  • Bump last_review_date in the front matter header if you reviewed the entire page.

[QuentinBisson]

@Rotfuks you probably want to check this out

[QuentinBisson]

I really like it overall but I'm wondering if we are not missing some important concepts like:

• it's plug and play, you can add your own data, dashbaords and so on
• that we eat our own dogfood (that we use it for ourselves for years)

Also, do we want to talk about the glue we make with our operators? And what about sloth? Maybe it's too specific :)

[pipo02mix]

Comments reviewed. @QuentinBisson I have included some mention to cover that two bullet points since I consider you were right ;)

For the operators, I will leave for a more tech doc entry (maybe tutorial or getting started)