Add support for GraalVM ResourceURLConnection

GraalVM native-image produces the binary with embedded resources from
jar:. The protocol is then substituted to resource:.

ring-core/src/ring/util/response.clj

@@ -289,6 +289,14 @@
     (if-not (zero? last-mod)
       (Date. last-mod))))
 
+(defmethod resource-data :resource
+  [^java.net.URL url]
+  ;; GraalVM resource scheme
+  (let [resource     (.openConnection url)]
+    {:content        (.getInputStream resource)
+     :content-length (connection-content-length resource)
+     :last-modified  (connection-last-modified resource)}))
+
 (defmethod resource-data :jar
   [^java.net.URL url]
   (let [conn (.openConnection url)]