Add basic flex tokens shape and mapping information

[JasonVMo]

Platforms Impacted

• targets all platforms but no runtime change right now

Description of changes

This is work generated from the design repository. It does the following:

• Create a basic react-native flex tokens shape. This matches the values that will be in newer web-specs or design resources going forward.
• These names/values also map to the token instructions for the various component specs that were merged in recently.

It also defines several mapping files, also encapsulating research and mapping work I did in that repository.

• maps color flex-tokens to fluent tokens (either alias, shadow, or global)
• maps non-color flex tokens to fluent tokens (generally global tokens)
• maps CSS names to these flex token names

Verification

Non-coding change