Create a github workflow/bot for parsing diagnostics in issues

When folks upload a "download diagnostics" to an issue, it would be helpful for a workflow to parse it and summarize some info in a subsequent post.

In particular, some of the stats being worked on in #363 and other useful info as things evolve.

This might be a good feature for someone who isn't across the wider project yet, but is keen to dig into something to start with.

- Parse the json from diagnostics
- Identify vital stats such as those discussed in #363 and surface them in a comment
- If a debug-enabled log file is included:
- Possibly anonamise and replace the log file (it includes mac and IP addresses)
- parse out:
- For each scanner, stats on adverts-per-second
- Summaries of adverts from each MAC address
- Identify exceptions/errors, possibly grouping them along with counts and stats