Add basic, anonymous telemetry which can be disabled with a command line argument

[timrogers]

This PR adds basic, anonymous telemetry to the extension to give the maintainers information about real-world usage. This data is limited to:

• The number of exports and imports being run
• The versions of GitHub Enterprise Server being used
• The versions of the extension currently in used

You can disable all telemetry by specifying the --disable-telemetry argument.

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🚀	This description was created by Ellipsis for commit 6ed3387

Summary:

Added anonymous telemetry to track usage metrics with an option to disable it via --disable-telemetry.

Key points:

• Added anonymous telemetry using posthog-node in src/commands/export.ts and src/commands/import.ts.
• Captures events export_start and import_start with GitHub Enterprise Server version and extension version.
• Introduced --disable-telemetry option to disable telemetry in both export and import commands.
• Updated README.md to document the new telemetry feature and --disable-telemetry option.
• Modified GitHub Actions workflow in .github/workflows/end_to_end_tests.yml to use --disable-telemetry.
• Added posthog-node dependency in package.json.
• Created src/posthog.ts to store PostHog API key and host.

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Generated with ❤️ by ellipsis.dev

[timrogers]

@ellipsis-dev review

[ellipsis-dev]

❌ Changes requested. Reviewed everything up to 6ed3387 in 36 seconds

More details

• Looked at 292 lines of code in 6 files
• Skipped 1 files when reviewing.
• Skipped posting 0 drafted comments based on config settings.

Workflow ID: wflow_i1yTOpPf0bENtQIM

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[ellipsis-dev]

The PostHog API key is hardcoded, which is a security risk. Consider using environment variables to store sensitive information securely.