chore(docs): add missing image updater command flags

[cjcocokrisp]

Fixes #1130

In this issue some of the command flags are missing in docs/install/reference.md. The following has been updated to better reflect the command flags.

• Added missing command flags with their descriptions to docs/install/reference.md, flags included:
  • applications-api
  • argocd-namespace
  • disable-kube-events
  • git-commit-email
  • git-commit-sign-off
  • git-commit-signing-key
  • git-commit-signing-method
  • git-commit-user
  • help
  • match-application-name
  • metrics-port
  • warmup-cache
• Included information about whether or not the command flag is linked to an environment variable
• Adjusted formatting so the flags appear in the same order as the CLI help command
• Fixed formatting with flag headers so the parameters appear italicized

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.34%. Comparing base (4c97b4b) to head (5b657f3).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1146   +/-   ##
=======================================
  Coverage   63.34%   63.34%           
=======================================
  Files          15       15           
  Lines        2357     2357           
=======================================
  Hits         1493     1493           
  Misses        769      769           
  Partials       95       95           

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[chengfang]

need to remove the space near the end. namespace looks good so let's keep it. So it will end like *token***

We've seen formatting issues with a space.

[chengfang]

same as above with the space

[chengfang]

same as above with the space

[chengfang]

same as above with the space

it should start with --argocd-namespace

[chengfang]

same as above with the space above and in other flags below.

[chengfang]

Thinking more of it, I think we should also add the missing top-level sub-commands like template, test, completion, etc to this page for completeness:

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  run         Runs the argocd-image-updater with a set of options
  template    Test & render a commit message template
  test        Test the behaviour of argocd-image-updater
  version     Display version information

[cjcocokrisp]

Sounds good, I will make these changes on Monday.

[cjcocokrisp]

Fixed the issues mentioned above and documented the rest of the commands.

The markdown file with all the commands was getting too big so I broke up them up each into their own pages. All of the pages are under the section title "Command Line and Configuration reference."