Bring CSGO/CS2 protobufs as library

[LossyDragon]

Description

Bring CSGO/CS2 protobufs in as a library, similar to javasteam-tf.

This has the same protobufs used in DoctorMcKay/node-globaloffensive, and is not a complete list of all CS related protos.

Checklist

• [x] Code compiles correctly
• [x] All tests passing
• [x] Samples run successfully
• [x] Extended the README / documentation, if necessary