Gauege chart added to fl_chart example but it seams it does not release in 1.2.0 version

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**Describe the bug**
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**To Reproduce**
Provide us a completely reproducible code (contains the main function) in a `main.dart` file, it helps us to find the bug immediately.

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**Versions**
- which version of the Flutter are you using?
- which version of the FlChart are you using?

The issue names no source file, test, or entry point. Start by comparing the Gauge chart example in the repository with the contents of the 1.2.0 package or release, then verify whether the example is included; done means the reported release discrepancy is confirmed or corrected.

Written by the indexing model from the issue text.