add Spoon in Google OSS-Fuzz

> OSS-Fuzz, Google’s open source fuzzing service, now supports fuzzing applications written in Java and other Java Virtual Machine (JVM) based languages (e.g. Kotlin, Scala, etc.). Open source projects written in JVM based languages can add their project to OSS-Fuzz by following our documentation.

Reference: https://security.googleblog.com/2021/03/fuzzing-java-in-oss-fuzz.html