initialize changelog for sqlproj ext

[dzsquared]

Pull Request Template – Azure Data Studio

Description

Standalone changelog.md for SQL projects extension, will populate in VS Code marketplace and local extension view.
#26273

Refs:

• https://code.visualstudio.com/api/working-with-extensions/publishing-extension#marketplace-integration
• as seen in https://marketplace.visualstudio.com/items?itemName=ms-azuretools.vscode-azurefunctions

Code Changes Checklist

• PM-level markdown changes
• New or updated unit tests added
• All existing tests pass (npm run test)
• Code follows contributing guidelines
• No UI regressions introduced
• Logging/telemetry updated if applicable
• Cross-platform support checked (Windows, macOS, Linux if relevant)

Reviewers: Please read our reviewer guidelines

[ssreerama]

So, we are going to remove this Unreleased section during the final release right?

[ssreerama]

Let's say we have couple more fixes but don't want to include them with the planned release, we still keep them here as the future info provided to the customers?