refactor: mark Github releases as pre-releases w/ Fastlane (#2574)

README.md

@@ -350,3 +350,5 @@ After this command line call, attach the latest build to the new version in the
 1. Wait at least a day for internal testers to report any blocking problems
 1. `bundle exec fastlane beta` to distribute the builds to external test groups in TestFlight and the Play Store
 1. After receiving OK during iteration meeting, make App Store release available
+    1. Start the staged release in App Store Connect
+    1. Mark the Github release as the latest non-pre-release

fastlane/Fastfile

@@ -449,7 +449,8 @@ lane :release do
       description: changelog,
       # This is really just a fallback in case last_tag isn't really a tag
       commitish: "main",
-      upload_assets: [apk_path]
+      upload_assets: [apk_path],
+      is_prerelease: true
     )
   end
   system "git checkout #{original_branch}", exception: true