Improve keyboard avoid behavior for section list and Screen component with "fixed" preset variant

[fpena]

Please verify the following:

• [x] yarn test jest tests pass with new tests, if relevant
• [x] yarn lint eslint checks pass with new code, if relevant
• [x] yarn format:check prettier checks pass with new code, if relevant
• [x] README.md (or relevant documentation) has been updated with your changes

Describe your PR

This PR solves an issue with text inputs inside a list (e.g. SectionList, Flatlist, etc). It was first reported here.

Overall behaviour

Here are also videos with examples of variants for Screen.tsx and its preset prop.

preset="fixed" - items at top	preset="fixed" - items at bottom	preset="scroll" - items at top	preset="scroll" - items at bottom