ios: add README file to ios/logs directory

Allows us to get rid of the `.gitkeep` file.

Signed-off-by: Jakub Sokołowski <jakub@status.im>

ios/logs/README.md

@@ -0,0 +1,14 @@
+# Description
+
+This directory is the destination of logs created by Fastlane and React Native Xcode script.
+
+# Logs
+
+* `react-native-xcode.log` - Output from `node_modules/react-native/scripts/react-native-xcode.sh`.
+  - Created by redirecting output of `shellScript` in `ios/StatusIm.xcodeproj/project.pbxproj`.
+* `Status PR-StatusImPR.log - Created by [Fastlane Gym](https://docs.fastlane.tools/actions/gym/).
+  - Configred via [`Fastfile`](../Fastfile) using `buildlog_path` argument for `build_ios_app`.
+
+# CI
+
+These log files are uploaded to Jenkins as CI job artifacts on failure using `archiveArtifacts`.