Platoons social functionality (#91)

### Description

This implements and completes #87 (to the best of my knowledge)

### Game

Robocraft

### Please confirm

- [x] I am the legal owner or represent the owner of all work submitted
- [x] I consent to my submission being added to this FOSS project
- [ ] This PR used LLMs to generate some or all of the code changes

Reviewed-on: https://git.ngram.ca/OpenJam/rc-servers/pulls/91
Co-authored-by: NG (Graham) <ngniusness@gmail.com>
Co-committed-by: NG (Graham) <ngniusness@gmail.com>

rc_social_room/src/data/mod.rs

@@ -2,3 +2,4 @@ pub mod friend;
 pub mod clan_invite;
 pub mod clan;
 pub mod custom;
+pub mod platoon;