Add "Table of Contents" to README.md

[TahaTesser]

Description

This PR introduces "Table of Contents" to the README.md file

Related Issues

fixes Include a "Table of Contents" in README

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 2b8ea54):

• https://coffeemakerexample--pr175-table-of-contents-xushvirl.web.app
• https://playgroundwoltexample--pr175-table-of-contents-2gfn4w6l.web.app
• https://playgroundnavigator2woltexample--pr175-table-of-conten-97v4s4hh.web.app

_{(expires Sun, 14 Apr 2024 17:25:01 GMT)}

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[ulusoyca]

👑 Thanks Taha!