Add support for Snowflake SQL.

[nevdelap]

I suspect it might just need this line in Parsing.Documents.fs...

    lang "SQL" "postgres" ".pgsql|.psql|.sql" <| sc [line "--"; cBlock]

duplicated as...

    lang "Snowflake SQL" "" ".sql" <| sc [line "--"; cBlock]

I have no idea about F# or dotnet and I'm on Linux without such things installed, otherwise I'd have a crack at testing it. (I see it is compiled down to Extensions.js where it is installed and I tried hacking at that just to see, but no good, as expected. 😉)

My workaround is to switch back and forth between Snowflake SQL and plain SQL when I want it to wrap a comment.

Thanks!