Add support for F# package reference + Fix CommentPreproc detection

[MangelMaxime]

Hello,

Disclaimer: I am new to Go, so I am unsure if what I did is all that is needed

This PR adds support for package reference syntax #r "nuget: PacakgeName".

https://docs.microsoft.com/en-us/dotnet/fsharp/tools/fsharp-interactive/#referencing-packages-in-f-interactive

In order, to have the package reference syntax working I had to move the CommentPreproc rule before the Operator.

I believe this is because inside of the Operator there is a match for # char which was preventing the CommentPreproc rule to handle it.

I also needed to no greedly capture the whole line to end otherwise it was capture the whole line as CommentPreproc instead of a mix of CommentPreproc and LiteralString for example.

[
  {"type":"CommentPreproc","value":"#nowarn \"9\""}
]

instead of

[
  {"type":"CommentPreproc","value":"#nowarn"},
  {"type":"Text","value":" "},
  {"type":"LiteralString","value":"\"9\""}
]

---

Because, I found it to be a dangerous change I decided to add "complex" F# code to serves as a base reference to check that I didn't break anything by mistakes.
The "complex" F# code has been added inside the file lexers\testdata\fsharp\fsharp.actual. That file is a copy coming from https://github.com/ionide/ionide-fsgrammar/blob/master/sample-code/SimpleTypes.fs which is a really robust reference as it is used since 5+ years as a base for the VSCode grammar testing.

If you look at this commit a3b894e you can see that my changes only impacted the wrongly highlighted CommentPreproc.

-  {"type":"Operator","value":"#"},
-  {"type":"Keyword","value":"if"},
+  {"type":"CommentPreproc","value":"#if"},

It changes from an invalid Operator detection to a CommentPreproc.

[alecthomas]

This is great, thank you.