Add IsLiteral / LiteralValue to FSharpField so that Enum tooltips in XS can have the literal values rendered.

[7sharp9]

Please add LiteralValues to FSharpField symbols. This will allow Enum tooltips to be rendered in XS, at them moment its not possible to extract a literal value from an FSharpField

They should be available via the following:

type FSharpField(g:TcGlobals, thisCcu, tcImports, d: FSharpFieldData)  =
    inherit FSharpSymbol (g, thisCcu, tcImports,  

...

    member __.IsLiteral = 
        if isUnresolved() then false else 
        d.RecdField.LiteralValue.IsSome

    member __.LiteralValue = 
        if isUnresolved() then None else 
        d.RecdField.LiteralValue

If this is ok then I can submit a PR...