Support F# code quotations

[zspitz]

https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/code-quotations

Meaning, having an extension method on Expr and Expr<T> which would produce strings in various formats: F# quotationed code, factory methods on Expr, perhaps others.

Can this be done in the existing library? It would mean either

• extending all the writer/visitors with overloads for Expr, or
• replacing the current overloads with some kind of adapter interface, which would have separate implementations for expression trees and code quotations.

Having a separate library would mean we couldn't reuse some of the existing writer/visitor functionality..