core: Tidy contributor onboarding, fix typos. (#12700)

core: Tidy contributor onboarding.

- Fixes typos.
- Fixes stale links.
- Tidies Makefile so that Poetry env is optional for hygiene commands.
- Remove mismatched YAML naming.
- Uses shebang on Python scripts.
- Document semver usage.
- Redirect OpenAPI schema.

Signed-off-by: Teffen Ellis <592134+GirlBossRush@users.noreply.github.com>

scripts/generate_config.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 """Generate config for development"""
 
 from yaml import safe_dump