Add an UnsupportedTabException exception class

This class makes easier for LinkHandlerFactory implementations to declare an
UnsupportedOperationException.

Author: AudricV

extractor/src/main/java/org/schabi/newpipe/extractor/exceptions/UnsupportedTabException.java

@@ -0,0 +1,7 @@
+package org.schabi.newpipe.extractor.exceptions;
+
+public final class UnsupportedTabException extends UnsupportedOperationException {
+    public UnsupportedTabException(final String unsupportedTab) {
+        super("Unsupported tab " + unsupportedTab);
+    }
+}