Create medicare-cardholders use case

[indexing]

• Adding new page for Medicare cardholders use case

[github-actions]

Coverage report

This PR does not seem to contain any modification to coverable code.

[github-actions]

Preview url: https://benefits-2306--cal-itp-previews.netlify.app

[indexing]

@thekaveman It seems I need to create this file first before adding content? The syntax for my Mermaid diagram, for example, isn't recognized when I added content to the file.

[machikoyasuda]

@indexing I think you are missing the file extension .md at the end of the file

[machikoyasuda]

Hey @indexing - The document looks great. This is the link to the preview: https://benefits-2306--cal-itp-previews.netlify.app/

As you can see, the sidebar title styles are not aligned:

I think it should be something like:

Introduction
Agency cardholders
Low-income
Medicare cardholders
Older adults
Veterans

The weird one is the Low-income adjective because it's not a noun/a name of a person like all the others. But we can leave that be. I think the Agency cardholders and Medicare cardholders titles should be formatted that way, and leave the use case part out.

The term use case here is a little confusing because there's this whole other Use cases section in the Product and design area: https://benefits-2306--cal-itp-previews.netlify.app/product-and-design/use-cases/enrollment-use-cases/

[machikoyasuda]

@indexing This change looks good to me. Maybe this PR can go out at the same time? #2253 The product and design phases are in progress now.