Markdown summary has strange output for * stack

[menehune23]

When summarizing a buildpack in markdown format, the result can be something like the following, when a * stack is included:

A couple of options:

• Wrap entries in a ` so that they are rendered literally (looks better for stack IDs anyway), OR
• Replace the entire list with - Any stack

Or even both, as the first option is a nice improvement anyway

Version: This behavior exists on the current version of jam as of this writing (v1.1.1).

[menehune23]

Put up a PR. I nixed the second bullet to keep it simple, and to keep it consistent with the JSON formatter.