Maintanence: Update README.md to improve DX

[salihgueler]

Description

Updates the README.md files to fix some problems explained at issue https://github.com/woltapp/wolt_modal_sheet/issues/284

Related Issues

https://github.com/woltapp/wolt_modal_sheet/issues/284

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth and quick review process.

• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [x] My PR includes tests for all changed/updated/fixed behaviors.
• [x] All existing and new tests are passing.
• [x] I updated/added relevant documentation (doc comments with ///).
• [x] The analyzer (melos run analyze) does not report any problems on my PR.
• [x] The package compiles with the minimum Flutter version stated in the pubspec.yaml

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• [ ] Yes, this is a breaking change.
• [x] No, this is not a breaking change.

[ulusoyca]

Thanks for this amazing work! Added some suggestions!