docs/integration: use adopters list from github

[tormath1]

I think the initial purposes of this doc was to reference any entities relative to Flatcar. This list is not maintained and it was even redirecting users to non-maintained website (like Deis).

Closes: flatcar/Flatcar#1224

[github-actions]

Azure Static Web Apps: Your stage site is ready! Visit it here: https://lemon-wave-085522403-285.westeurope.1.azurestaticapps.net

[jepio]

or maybe we should list the integrations that we know work? like falco,capi, more?

[tormath1]

I'm a bit confused by the original intention of this section as it mixes users with cloud providers: Deis seemed to be a user while cloud providers are just... cloud providers.
Maybe we should list users (https://github.com/flatcar/Flatcar/blob/main/ADOPTERS.md#who-is-using-flatcar) + third party projects:

• CAPI
• Typhoon
• Falco
• ...

but then it would duplicate with other section (https://www.flatcar.org/docs/latest/container-runtimes/getting-started-with-kubernetes/#cluster-api)

[nocheinlarry]

I can copy @tormath1 impression, not getting the intention of the flatcardocs..integration, the proposed solution having just one place for naming adoptors in ADOPTERS.md is a good solution and makes it much clearer in the docs. The new updated integrations site (https://lemon-wave-085522403-285.westeurope.1.azurestaticapps.net/docs/latest/reference/integrations/) looks good. Thanks @tormath1.

[jepio]

I'm fine merging this as is but adopters != integrations. Adopters are end-users and integrations are other (open source) projects that have native support for Flatcar in some way. You'll note that none of the integrations proposed above (CAPI, typhoon, falco, kOps) are in adopters. We could use a list of projects that we know have good support for Flatcar.