docs: helix (#101)

Co-authored-by: Mitchell Hanberg <[email protected]>

README.md

@@ -42,6 +42,20 @@ Using eglot:
 (add-hook 'heex-ts-mode-hook 'eglot-ensure)
 ```
 
+</details>
+</li>
+<li>
+<details>
+<summary>Helix</summary>
+
+Add the following config to your `~/.config/helix/languages.toml`.
+
+```toml
+[[language]]
+name = "elixir"
+scope = "source.elixir"
+language-server = { command = "path/to/next-ls", args = ["--stdio=true"] }
+```
 </details>
 </li>
 </ul>