CU-9rrjbq Menu changes preparing for content specific to 1.0

[raulraja]

• Removes references to incubator
• Removes links to articles that where mostly encoded in terms of Kinds (to be reviewed in content PRs if content remains relevant)
• Introduces Training && Support links currently pointing exclusively to 47 Degrees until other companies also want to announce themselves there. /cc @garthgilmour Not sure if Instil is offering Arrow trainings and would like to also be featured here in a dropdown link menu.
• Rearranges menus in core, fx and optics to be consitent.
• Adds link to suspend () -> A in types in Fx pointing to IO removal docs in favor of suspend

[franciscodr]

Task linked: CU-9rrjbq Polish current documentation to remove obsolete items

[nomisRev]

Looks good to me. A couple entries for Arrow Fx can be removed due to deprecation. I only reviewed the content for the website. I'm not very familiar with Jekyll or JS.

[nomisRev]

I cannot add multiline suggestions for code that wasn't modified it seems.

ConcurrrentVar, Promise & Semaphore are deprecated in favor of KotlinX versions of these data types. KotlinX has the following types with the same semantics: Channel(), CompletableDeferred() and Semaphore(..).

[rachelcarmena]

Thanks @nomisRev !!