Add julia support (LSP not working)

[bottine]

I took the treesitter recipes from here: https://github.com/nvim-treesitter/nvim-treesitter/tree/master/queries/julia
and the command for the LSP is from: https://github.com/julia-vscode/LanguageServer.jl/wiki/Kakoune

I can't make the languageserver work, but this is maybe because I can't make it work in general.

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Got the following log:

2021-07-05T10:55:54.618 mio::poll [TRACE] registering event source with poller: token=Token(1), interests=READABLE | WRITABLE
2021-07-05T10:55:54.618 mio::poll [TRACE] registering event source with poller: token=Token(2), interests=READABLE | WRITABLE
2021-07-05T10:55:54.618 mio::poll [TRACE] registering event source with poller: token=Token(3), interests=READABLE | WRITABLE
2021-07-05T10:55:54.618 helix_lsp::transport [INFO] -> {"jsonrpc":"2.0","method":"initialize","params":{"capabilities":{"textDocument":{"completion":{"completionItem":{"snippetSupport":false},"completionItemKind":{}},"hover":{"contentFormat":["markdown"]}},"window":{"workDoneProgress":true}},"processId":48451,"rootUri":"file:///path/to/Folder"},"id":0}
2021-07-05T10:55:56.620 mio::poll [TRACE] deregistering event source from poller
2021-07-05T10:55:56.620 mio::poll [TRACE] deregistering event source from poller
2021-07-05T10:55:56.620 mio::poll [TRACE] deregistering event source from poller
2021-07-05T10:55:56.620 mio::poll [TRACE] registering event source with poller: token=Token(0), interests=READABLE
2021-07-05T10:55:56.620 mio::poll [TRACE] registering event source with poller: token=Token(1), interests=READABLE

[pickfire]

I didn't test this but I think highlighting should be working to some extent. Since you tried it out so it should work better than no support. Will merge once it passes the tests.