Add custom modal type examples to the playground app

[ulusoyca]

Description

This PR adds two examples for adding custom modal types:

Floating Bottom Sheet Type
floating_bottom.mov

Top Notification Sheet Type
top_noti_s.mov

Related Issues

Replace this paragraph with a list of issues related to this PR from the issue database. Indicate, which of these issues are resolved or fixed by this PR.

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.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes tests for all changed/updated/fixed behaviors.
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (melos run analyze) does not report any problems on my PR.
• 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.
• No, this is not a breaking change.

[github-actions]

Visit the preview URL for this PR (updated for commit 37b764e):

• https://coffeemakerexample--pr241-add-custom-modal-exa-lgaffy4x.web.app
• https://playgroundwoltexample--pr241-add-custom-modal-exa-kpazdfg7.web.app
• https://playgroundnavigator2woltexample--pr241-add-custom-moda-j6r6lih8.web.app
• https://coffeemakernavigator2--pr241-add-custom-modal-exa-rh6xg9pk.web.app

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