fix: use correct Lua syntax

docs/3.editor-integrations.md

@@ -20,10 +20,10 @@ Vento syntax highlighting is available for Neovim through
 
 To use it, add the "vento" filetype
 
-```js
+```lua
 vim.filetype.add({
-  extension: {
-    vto: "vento",
+  extension = {
+    vto = "vento",
   },
 });
 ```
@@ -34,7 +34,7 @@ And install the "vento" parser with `TSInstall`, or add it to the
 It's also recommended to install "javascript" and "html" parsers to get better
 syntax highlighting inside vento files.
 
-```js
+```lua
 require("nvim-treesitter.configs").setup({
     ensure_installed = { "vento", "html", "javascript", "..." },
 })