Update README: add `static` to `ThreadLocal` example
Update README: add `static` to `ThreadLocal` example

Closes #420

xfrendx/kryo,EsotericSoftware/kryo,xfrendx/kryo,magro/kryo,EsotericSoftware/kryo,magro/kryo,EsotericSoftware/kryo,EsotericSoftware/kryo