Add FSharpOption support

[MrLuje]

Fixes #913

Add support for serialization/deserialization of FSharpOption<> type

I may have missed some usecases, but here's what I though of:

• scalar & objects types (regular enumerable should work OOB from what I see)
• DefaultValue is not really a thing for F# record, so out of scope
• DefaultValuesHandling works

[aaubry]

This feature has been released in version 15.3.0.