OS Version and Compatability Guide for Insomnia

Inspired by [this ticket](https://konghq.atlassian.net/browse/INS-564)... let's start with a basic versions and compatibility chart.

- We release ~2 major versions per year.
- We support a major version for at least 2 years against any critical defect or critical vulnerability.
- We do not roll new features back to old versions - in general Insomnia uses browser-style versioning and clients should aim to be on the newest version.
- We release minor versions every 2-4 weeks.
- New features are always in minors/majors.
- We release patches as necessary.

I'm not the best source of truth for what OS versions we support, but see Jira linked above and [this slack thread](https://kongstrong.slack.com/archives/C08E26ZEPL2/p1749205472805939?thread_ts=1749113806.848709&cid=C08E26ZEPL2).

Tag Cam again when done, so we can update the download page to link to this.