Fix maintainVisibleContentPosition calculations and add tests + docs … #406

Job	Run time
determine_mode	5s
set_hermes_version	-1s
publish_bumped_packages	2m 5s
prebuild_apple_dependencies	-1s
build_android	-1s
prebuild_react_native_core	-1s
publish_react_native	-1s
post_publish	0s
bump_podfile_lock	0s
generate_changelog	0s
create_draft_release	0s
	2m 5s

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