Document all supported application annotations for configuring argocd-image-updater

[chengfang]

Is your feature request related to a problem? Please describe.
A complete list of all supported application annotations for configuring argocd-image-updater will be helpful. A good place seems to be this section: https://argocd-image-updater.readthedocs.io/en/latest/configuration/applications/
 
https://argocd-image-updater.readthedocs.io/en/latest/configuration/images/#appendix contains such info. Need to double check if it's complete and accurate.

Describe the solution you'd like
add such info, probably as a table that lists all supported annotations, whether it's per-image, or application wide, description of usage, and examples.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.