Revert "fix(deps): update dependency is-html to v3"

This reverts commit 270b5a6.

Author: julianlam

package.json

@@ -27,7 +27,7 @@
   },
   "dependencies": {
     "async": "^3.2.0",
-    "is-html": "^3.0.0",
+    "is-html": "^2.0.0",
     "markdown-it": "^12.0.0",
     "node-quill-converter": "^0.3.2",
     "quill": "^1.3.6",