Document reanalyzing feature, and include rayhunter-check in release

doc/reanalyzing.md

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+# Re-analyzing recordings
+
+Every once in a while, Rayhunter refines its heuristics to detect more kinds of
+suspicious behavior, and to reduce noise from incorrect alerts.
+
+This means that your old green recordings may actually contain data that is now
+deemed suspicious, and also old red recordings may become green.
+
+You can re-analyze any old recording inside of Rayhunter by clicking on "N
+warnings" to expand details, then clicking the "re-analyze" button.
+
+## Analyzing recordings on Desktop
+
+If you have a PCAP or QMDL file but no rayhunter, you can analyze it on desktop
+using the `rayhunter-check` CLI tool. That tool contains the same heuristics as
+Rayhunter and will also work on traffic data captured with other tools, such as
+QCSuper.
+
+You need Rust installed and the rayhunter repository checked out:
+
+```sh
+cargo run -p rayhunter-check -- --path ~/Downloads/myfile.qmdl
+cargo run -p rayhunter-check -- --path ~/Downloads/myfile.pcap
+```
+
+Since, 0.7.0, `rayhunter-check` is included in the release zipfile.