Merge pull request #302 from textpattern/dependabot/npm_and_yarn/prismjs-1.21.0

Bump prismjs from 1.20.0 to 1.21.0

Author: philwareham

package.json

@@ -33,7 +33,7 @@
   "dependencies": {
     "easeljs": "1.0.2",
     "preloadjs": "1.0.1",
-    "prismjs": "1.20.0",
+    "prismjs": "1.21.0",
     "textpattern-branding": "0.2.11",
     "tweenjs": "1.0.2"
   },