Syntax highlight for graphql_ppx

[Huxpro]

Hey! This PR adds the syntax highlight for GraphQL_PPX!
The graphql grammar was shamelessly borrowed from graphql-for-vscode (or vscode-graphql, they're the same). So the color for GraphQL queries would be usually same with static *.graphql file. It actually did pretty bad in graphql variables tho. :(

The highlight for [%graphql] attributes and {||} are customized in my personal taste by using a monolithic string-ish color. So they won't be too poped out ;)

[ghost]

Thanks for the PR!

I think it would be nice to merge this into the extension but I don't quite understand why we want to duplicate the graphql highlighting here rather than relying on the existing plugin for that (via "include"). Are you saying you wanted to do that just to customize the scopes for different colorization than the other one uses?

[Huxpro]

@freebroccolo I was thinking of adding it to graphql one as well and personally I had no opinion with either. But I found we actually got more than one graphql-plugin in the market 😅 (so we dont need to depend on one and ask user to install it)

Another advantage might be that it's easier to customize it for reason needs. (e.g. adding new pattern, make the highlight more compatible with reason).

[ghost]

@Huxpro thanks for the clarification.

Honestly, I would prefer to avoid including the basic graphql highlighting in this plugin. I understand your point about the flexibility but it's going to mean more maintenance and it's something I don't use so that doesn't seem like an ideal combination. I'd also like to retain as much compatibility with other existing graphql extensions as possible.

I'd like to investigate the situation further by looking at the other extensions but it's going to be a couple of weeks before I have time to do it properly (currently very busy with work stuff). Just wanted to mention that so it doesn't seem like I'm ignoring this PR.

[zhangchen91]

jump into graphql?