Add: SagerNet

• The app complies with the inclusion criteria
• The original app author has been notified
• All related fdroiddata and RFP issues have been referenced in this merge request
• The upstream app source code repo contains the app metadata
• Builds with fdroid build ( https://gitlab.com/nekohasekai/fdroiddata/-/jobs/1285084509 )
• Releases are tagged

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Closes rfp#1719 (closed)