Consider supporting `efm-langserver` as alternative to archived null-ls

[ModProg]

This would be cross-editor compatible and even be a preliminary solution for #1 with https://marketplace.visualstudio.com/items?itemName=Matts966.efm-langserver-vscode.

null-ls appears to be discontinued

[ModProg]

This "support" would be similar to null-ls by just providing a config file.

[ModProg]

languages:
  rust:
    - lint-formats: ["%l,%c,%e,%k,%m"]
      lint-stdin: false
      lint-severity: 2
      lint-ignore-exit-code: true
      lint-command: |
        languagetool-code-comments check -f ${INPUT} -l en-US | jq -r '.[] | [.moreContext.line_number, .moreContext.line_offset + 1, .moreContext.line_number, .moreContext.line_offset + .context.length + 1, "\(.message) Try: \(.replacements | map(.value) | join(", "))"] | join(",")"'

This is diagnostics working, I might look at code actions as well at some point.

[dustinblackman]

Amazing! Great work!

I may try to chip in if I can allocate time, otherwise I'll gladly accept a PR. Thanks!