Add usage page for F#

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Using EF from F# requires several specific patterns that differ from C#, and wouldn't be obvious to a beginner. We should age a page summarizing those things.

• DbSet auto-initialization is not supported (because of how F# works) - people need to explicitly initialize their DbSet properties (see #34356).
• Use EF.Parameter() for parameterization (see #12841)
• Use the external EFCore.FSharp package, especially for migrations and scaffolding (see discussion)