Add functional interfaces

src/main/java/org/kohsuke/github/function/InputStreamFunction.java

@@ -0,0 +1,12 @@
+package org.kohsuke.github.function;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * A functional interface, equivalent to {@link java.util.function.Function} but that allows throwing {@link Throwable}
+ *
+ */
+@FunctionalInterface
+public interface InputStreamFunction<R> extends FunctionThrows<InputStream, R, IOException> {
+}