fix: Add error handling for unknown serve commands in serveCmd function

[damiant]

This pull request updates the extension to version 2.1.3 and improves error handling when the serve command cannot be determined for a web project. The main changes focus on providing clearer feedback to users and preventing repeated error messages.

Error handling improvements:

• Added logic to display a user-friendly error message in the VS Code UI when the serve command cannot be determined, and ensured the message is only shown once per session (src/web-run.ts).
• Improved logging by showing output and providing a more descriptive error message when no serve/start/dev scripts are found in package.json (src/web-run.ts).
• Imported the showOutput function from logging to support enhanced error feedback (src/web-run.ts).
• Added a serveUnknownMsg flag to prevent repeated error messages during the same session (src/web-run.ts).

Versioning:

• Bumped the extension version to 2.1.3 in package.json and documented the change in CHANGELOG.md. [1] [2]