Interactive API client customization UI

[danopia]

Most important feature is showing a list of API actions and letting the user manually check individual ones and/or add glob patterns and show which/how many actions the globs are including.

• Documentation selection level (none/short/full)
• Checkboxes for waiters and paginators - should be good with just toggling whether they are emitted overall, and as now they'll only emit if the action they wrap is also emitted
• List of checkboxes or similar for all actions
• Text Input[s] for action name globs, which dynamically check & gray out all matching actions in the above list
• Button to load the new file and display the file size
• Download button (gives .ts)
• Should be accessible & pre-filled from any URL that can be imported into Deno
• Can depend on Javascript :)