[In_app _purchase] README excerpt examples and changelog

[gerardomorales88]

Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.

List which issues are fixed by this PR. You must list at least one issue.

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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Test plan

• dart run script/tool/bin/flutter_plugin_tools.dart update-excerpts --packages=quick_actions — no diff after regeneration
• dart run script/tool/bin/flutter_plugin_tools.dart validate --packages=quick_actions — no issues
• flutter analyze in example/ — no issues
• dart format --output=none --set-exit-if-changed on the new excerpts file — no changes needed
• flutter test in the package — all tests pass

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Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩²

[gemini-code-assist]

Code Review

This pull request updates the in_app_purchase package's README examples and documentation excerpts to match the current package API, introducing a new readme_examples.dart file to house these code snippets. Feedback on the new file highlights several potential runtime issues, including missing platform guards for iOS/macOS-specific platform additions, a potential out-of-bounds index error when reading transactions, and unsafe null assertions on subscription details for non-subscription products.