Adding fp8 to ukernel documentation

[vpirogov]

This PR documents fp8 support in ukernel API.

Bonus typo fixes:

• Missing spaces in ISA descriptions
• Wording in developer guide index

[ranukund]

Functional API - the terminology hasn't been promoted or described in the documentation yet (apart from Examples and Tutorials); the key concepts section doesn't mention that the core API is called the functional API. We can have an overview page under "Learn" module and describe the APIs (functional and graph). Should the "Functional API" naming be promoted without any prior context? My two cents.

[vpirogov]

Functional API - the terminology hasn't been promoted or described in the documentation yet (apart from Examples and Tutorials); the key concepts section doesn't mention that the core API is called the functional API. We can have an overview page under "Learn" module and describe the APIs (functional and graph). Should the "Functional API" naming be promoted without any prior context? My two cents.

With the new documentation structure we need a term to identify "classical" oneDNN API and differentiate it from Graph and ukernel. Specifically the following content is covering "classical" API:

• Key Concepts
• Basic Workflow
• oneDNN concepts
• Supported primitives

"Functional API" is a term that I would use, but I'm open to suggestions.

+@uxlfoundation/onednn-arch for additional input