Find better solution to show the historic reliability of the public instances

[tdulcet]

send-instances/README.md

Lines 9 to 10 in 0895cad

	This page does not give any promises or warranties with regard to instance
	security and reliability.

Consider setting up something like Upptime (https://github.com/upptime/upptime) to automatically show the historic reliability (e.g. the uptime percentage) of all the public Send instances listed on the README, similar to how the server version is currently shown with a badge. Upptime specifically does the checking entirely with GitHub Actions, so it seemed like it could be a good choice for this, but there are of course many online services such as Uptime Robot that have an API and could potentially be used instead.

Anyway, this would allow users to make a more informed choice when selecting which Send instance to use with your ffsend CLI or my "FileLink provider for Send" add-on. It could also allow you to more quickly remove any dead instances from the list (#30).

[tdulcet]

For a temporary solution, I created this page where users can monitor the reliability the Send instances listed on the README over the last 90 days: https://stats.uptimerobot.com/5917xHMX01. Users can also click each instance on for more information. I just set this up yesterday, so it only has around ~1 day worth of data so far, but this will of course improve over time until it reaches the full 90 days.

While we work on a better long-term solution, I will try to keep the instances on this page in sync with any changes made to the list on the README... Note that shields.io does support Uptime Robot, so we could add badges to the README for this. I would be happy to submit a PR if this would be acceptable.