Convert roam namespaces to cljs

The clj functionality was only for tests and those tests no longer
exist for clj. Also removed unused dependency

src/main/frontend/external.cljs

@@ -0,0 +1,17 @@
+(ns frontend.external
+  (:require [frontend.external.roam :refer [->Roam]]
+            [frontend.external.protocol :as protocol]))
+
+(defonce roam-record (->Roam))
+
+(defn get-record
+  [type]
+  (case type
+    :roam
+    roam-record
+    nil))
+
+(defn to-markdown-files
+  [type content config]
+  (when-let [record (get-record (keyword type))]
+    (protocol/toMarkdownFiles record content config)))