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>

.github/codespell-words.txt

@@ -1,7 +1,32 @@
+akadmin
+asgi
+assertIn
+authentik
+authn
+crate
+docstrings
+entra
+goauthentik
+gunicorn
+hass
+jwe
+jwks
 keypair
 keypairs
-hass
-warmup
+kubernetes
+oidc
 ontext
+openid
+passwordless
+plex
+saml
+scim
 singed
-assertIn
+slo
+sso
+totp
+traefik
+# https://github.com/codespell-project/codespell/issues/1224
+upToDate
+warmup
+webauthn