feat: add table of cli flags to getting started guide

[allending313]

• Identified the issue which this PR solves.
• Read the CONTRIBUTING document.
• Code builds clean without any errors or warnings.
• Added appropriate tests for any new functionality.
• All new and existing tests passed.
• Added comments in the code, where necessary.
• Ran make check to catch common errors. Fixed any that came up.

Description:
Adds table to the getting started markdown with:

• All available command line flags
• Corresponding environment variables for each flag
• Clear and concise descriptions for each flag and variable

Which issue(s) this PR fixes:
Fixes #3023

Screenshots:

[mastercactapus]

Looks great!

There are a few that are the main ones to be used, can we move those to the top?

• --db-url and --db-url-next
• --public-url
• --data-encryption-key and --data-encryption-key-old

Also because those are listed as the primary ones by this guide:

To run GoAlert, you can start the binary directly, or from a container image. You will need to specify the --db-url, --public-url, and --data-encryption-key you plan to use.

[andrewbenington]

LGTM!

[mastercactapus]

I like the bold, but maybe --db-url-next and --data-encryption-key-old should not be (still at the top). We don't want to imply they should ever be used except in certain circumstances. Maybe append to the description of each (flag and table) something like "only use this when performing a switchover" and "only necessary when changing --data-encryption-key" respectively.

That way, the bold flags are the ones you need to use always, and the additional context will prevent confusion for new users.

[andrewbenington]

👍