docs: add some existing conventions to the docs style guide

[agilgur5]

Motivation

These are existing conventions that we try to follow most of the time and I figured it would be better to have a centralized link for these. I would previously say "conventionally" / "by convention" or "consistently" / "to be consistent" or link to a past example during review, but having a single source-of-truth is better.

Modifications

note a few that have recently been mentioned off the top of my head:

• relative links
  • Examples: docs: Add more readable argo CLI installation guide. Fixes #11750 #11751 (comment), build: support TLS for UI and Server with make start #13674 (comment), etc
• "Argo" vs. "Argo Workflows"
  • Examples: docs: add 3.6 upgrading notes for postgres archive and ARGO_TEMPLATE #13803 (comment), feat(artifacts): support ephemeral credentials for S3. Fixes #5446 #12467 (comment), etc
• In-line version annotations
  • Internal Examples: docs: consistently use "> v{version} and after" #12581 and its many back links, docs: in-line versioning + deprecation for multi-semaphore #13645, docs: Add some more info to the Scaling Doc #11731 (comment), etc
  • External Examples: https://kubernetes.io/docs/contribute/style/style-guide/#avoid-statements-that-will-soon-be-out-of-date (upstream style guide), https://v1-30.docs.kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/#serviceaccount-token-volume-projection (upstream), https://github.com/kubernetes/kops/blob/daea619a5980495778fc5ea5e652a277c9433fcb/docs/networking/cilium.md?plain=1#L30 (upstream-ish), https://argo-cd.readthedocs.io/en/release-2.12/user-guide/sync-waves/ (sibling), https://www.postgresql.org/docs/9.2/datatype-json.html (dependency), etc
• embedded example files
  • Examples: e.g. docs: in-line versioning + deprecation for multi-semaphore #13645

Verification

make docs passes

Future Work

1. add more existing conventions