[feature] markdown syntax highlighting of description

[masukomi (a.k.a. Kay Rhodes)]

I've been using markdown in my description blocks in v2, because it looks great when exported to a static blog, and is very readable when you run tooloo show <command>

But it would be much nicer if we had actual syntax highlighting like that provided by the following projects:

• Charm's glamour (go)
• bat (rust)
• termd (typescript)

I don't believe there is currently a Raku library that provides this.

Short term hacky fix

Check if glow is installed (Charm's cli wrapper around glamour), give it a tempfile to render, and insert the output into our output.

Long term fix

Port Glamor (or similar) to Raku, and use that.