chore: add prettier and format all files

- Install prettier ^3.6.2
- Add .prettierrc with project formatting rules
- Add .prettierignore to exclude generated files and dependencies
- Add npm scripts: format and format:check
- Format all files with prettier

tree-sitter.json

@@ -5,15 +5,9 @@
       "camelcase": "Shellspec",
       "scope": "source.shellspec",
       "path": ".",
-      "file-types": [
-        "shellspec"
-      ],
-      "highlights": [
-        "queries/highlights.scm"
-      ],
-      "locals": [
-        "queries/locals.scm"
-      ],
+      "file-types": ["shellspec"],
+      "highlights": ["queries/highlights.scm"],
+      "locals": ["queries/locals.scm"],
       "injection-regex": "shellspec"
     }
   ],