Add Syntax Documentation to vscode

[PizieDust]

closes #1312

This PR adds a new GUI option for Syntax Documentation to this vscode extension.

This PR depends on ocaml/ocaml-lsp#1218 which is unmerged.

We can activate this feature using OCAMLLSP_ENABLE_SYNTAX_DOCUMENTATION in extraEnv or via ocaml.server

{
    "ocaml.server.extraEnv":{
        "OCAMLLSP_ENABLE_SYNTAX_DOCUMENTATION": "false"
    },
    "ocaml.server.syntaxDocumentation": false,
}

cc @voodoos @pitag-ha

[smorimoto]

Could you add a change log entry and run the code format?

[PizieDust]

Could you add a change log entry and run the code format?

Thanks, done in the newest commits.

[voodoos]

Thanks @PizieDust, looks good :-)

[mnxn]

The lint-fmt check is still failing. I think you need to format again.

[voodoos]

@smorimoto I am not familiar with the interactions between the plugin and the server: what happens if a version of the plugin with this new configuration option is released but the server does not understand it ? (We still have to merge the Merlin PR and release it before merging the lsp-server one.) Will the option be shown even if it is not functional yet ?

[smorimoto]

It's shown even if it's not functional yet, but it doesn't cause the server to crash, so nothing should happen with this now.