[splashscreen docs] Update manual steps and inform about faulty cli (#7844)
[splashscreen docs] Update manual steps and inform about faulty cli (#7844)

* [splashscreen] README: Clarify step in manual build for Android

Add a code snippet I wish I had seen to not stumble over this step and to know exactly which lines to add here.

* Improve notes on faulty expo-splash-screen cli for Android

* Apply suggestions from code review

Co-authored-by: Brent Vatne <42801ce9f95fc47cedcf3521ed197f2c349c12e2@gmail.com>
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