Use makeup_graphql to get GraphQL syntax highlighting in docs

[Billzabob]

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Docs after:

[benwilson512]

Very cool! What remains to take this beyond draft?

[Billzabob]

I'm using the master version of ex_doc in this because it doesn't work without the fix that @josevalim added here. So once there is a release for that I'll change this to actually use the latest version of ex_doc instead of using the git option and this will be good :)

[josevalim]

0.25.2 is out :)

[Billzabob]

This is good to go 👍

[benwilson512]

Thank you!