Bring repository up to community standards

[NiceAesth]

• [x] Add code of conduct (https://github.com/osuAkatsuki/bancho.py/pull/383)
• [x] Add security policy (https://github.com/osuAkatsuki/bancho.py/pull/381)
• [x] Add issue templates (https://github.com/osuAkatsuki/bancho.py/pull/380)
• [x] Add pull request templates (feat, bug, etc.) (https://github.com/osuAkatsuki/bancho.py/pull/380)
• [ ] Add contributing guidelines
• [ ] Add code style guidelines (documentation in general)
• [x] Document breaking changes in wiki
• [x] Create language picker in wiki

[NiceAesth]

@jacksonisiah

[cmyui]

nice work on this, so quickly