Add `url-only` option, and do close HTTPS connections

Update a couple of dependencies

Fix breakage caused by the GitHub REST API upgrade

A couple of dependencies were updated.

This Action now uses node.js 20

This Action now uses the current `html-to-md`

This Action now uses node.js v16 and html-to-md

v0.0.3

This GitHub Action now handles feeds with title-less items gracefully.
Such feeds include the ones generated from GitHub's wikis.

Better title generation for aggregate tickets

Instead of using the current time as the label for aggregate tickets, we
now use "<N> new items" if more than one new item was found, and if only
one new item was found, we use the title of that item.

Prevent aggregate issues from being added multiple times

Our "was this ticket already opened?" check did not handle aggregate
issues correctly.