add missing dep

Author: Brad Cornes

packages/tailwindcss-language-server/package.json

@@ -22,6 +22,7 @@
     "emmet-helper": "0.0.1",
     "glob-exec": "^0.1.1",
     "line-column": "^1.0.2",
+    "tailwindcss-class-names": "0.0.1",
     "typescript": "^3.8.3",
     "vscode-languageserver": "^5.2.1",
     "vscode-uri": "^2.1.1"