fix(deps): add missing buffer dependency

Author: cwillisf

package-lock.json

@@ -57,6 +57,7 @@
     "arraybuffer-loader": "^1.0.6",
     "atob": "^2.1.2",
     "btoa": "^1.2.1",
+    "buffer": "^6.0.3",
     "canvas-toBlob": "^1.0.0",
     "decode-html": "^2.0.0",
     "diff-match-patch": "^1.0.4",