AK: Make StringView hashable

Author: https://github.com/mattco98
Commit: 67f2301150
Pull-request: https://github.com/SerenityOS/serenity/pull/3724
Issue: https://github.com/SerenityOS/serenity/issues/3714
Reviewed-by: https://github.com/linusg

AK/StringView.h

@@ -187,6 +187,11 @@ private:
     size_t m_length { 0 };
 };
 
+template<>
+struct Traits<StringView> : public GenericTraits<String> {
+    static unsigned hash(const StringView& s) { return s.hash(); }
+};
+
 }
 
 using AK::StringView;