Add type hints for GraalVM

[ivarref]

Hi

And thanks for a fine project!

When using clj-http-lite with GraalVM 19.3, I'm getting a strange stacktrace exception:

JVM Exception: #error {
 :cause java.net.URLEncoder
 :via
 [{:type java.lang.ClassNotFoundException
   :message java.net.URLEncoder
   :at [com.oracle.svm.core.hub.ClassForNameSupport forName ClassForNameSupport.java 60]}]
 :trace
 [[com.oracle.svm.core.hub.ClassForNameSupport forName ClassForNameSupport.java 60]
  [java.lang.Class forName DynamicHub.java 1197]
  [clojure.lang.RT classForName RT.java 2204]
  [clojure.lang.RT classForName RT.java 2213]
  [clj_http.lite.util$url_encode invokeStatic util.clj 28]
  [clj_http.lite.client$generate_query_string$fn__1889 invoke client.clj 150]
...

Adding these type hints solves this problem.

Would that be OK to include in the project?

Thanks
Kind regards

[martinklepsch]

Thanks for testing this with Graal and opening a PR, I'll cut a new release now :)