Add .gql extension to queries and fragments files

[diegosz]

If allowed queries and fragments files have a .gql extension we could have syntax highlighting.
When reading, GraphJin could ignore the file extension so it's backward compatible.
Any comment?

[dosco]

I do have the variables in the queries file (Needed for mutations) I hope those don't break syntax highlighting.

[diegosz]

yes, right, at least on vscode the syntax works perfect: