add npm deps

Author: Bruce Hauman

src/deps.cljs

@@ -6,4 +6,7 @@
    :provides ["devcards-marked"]
    :global-exports {devcards-marked DevcardsMarked}}]
  :externs ["devcards/js_libs/highlight.ext.js"
-           "devcards/js_libs/marked.ext.js"]}
+           "devcards/js_libs/marked.ext.js"]
+ :npm-deps {"create-react-class": "15.6.3",
+            "react": "16.13.1",
+            "react-dom": "16.13.1"}}