runtime(graphql): contribute vim-graphql to Vim core

runtime(graphql): contribute vim-graphql to Vim core

Contribute the core of my vim-graphql project (ftplugin, indent, syntax)
to the Vim project. This replaces the basic ftplugin support that was
already in the runtime with a more complete set of filetype settings. I
can assume maintainership for all of these files.

I'll continue to maintain the higher-level embedded filetype support
separately (in vim-graphql) for now, because it's fairly complex, but we
can consider integrating that code directly into vim later.

runtime files use the MIT license.

closes: #16273

Signed-off-by: Jon Parise <jon@indelible.org>
Signed-off-by: Christian Brabandt <cb@256bit.org>