Add support for GraalVM ResourceURLConnection

GraalVM creates a resource substitution for regular resources on SubstrateVM
@see https://github.com/oracle/graal/blob/db22885e2deb21ff0c1a72314f7b9bb86b7d334c/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/resources/ResourceURLConnection.java#L38

Differences between regular URLConnection & ResourceURLConnection:
- `resource:` - protocol instead of `jar:` or `file:`
- no way of checking if the resource is a directory

Author: kwojcik-blockether

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)]