AK: Add roundtrip fuzzer for Base64

Author: https://github.com/Janiczek
Commit: b56e022ce8
Pull-request: https://github.com/SerenityOS/serenity/pull/21618
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/timschumi ✅

Userland/Utilities/test-fuzz.cpp

@@ -13,6 +13,7 @@
 // TODO: Look into generating this from the authoritative list of fuzzing targets in fuzzer.cmake.
 #define ENUMERATE_TARGETS(T) \
     T(ASN1)                  \
+    T(Base64Roundtrip)       \
     T(BLAKE2b)               \
     T(BMPLoader)             \
     T(Brotli)                \