add missing dep

Author: Brad Cornes

packages/tailwindcss-language-server/package.json

@@ -19,6 +19,7 @@
     "@zeit/ncc": "^0.22.0",
     "css.escape": "^1.5.1",
     "dlv": "^1.1.3",
+    "emmet-helper": "0.0.1",
     "glob-exec": "^0.1.1",
     "line-column": "^1.0.2",
     "typescript": "^3.8.3",