Add telemetry for Qt Extension for VS Code

What is the benefit? Why is this valuable?

We should know which features from the Qt Extension for VS Code is used.

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What are common use cases?

• Get number of unique users on feature level
• Visualise results in PowerBI

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Technical information

• VS Code Extension Telemetry APIs can be used: https://code.visualstudio.com/api/extension-guides/telemetry

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