Home page opens in every VS Code window

[JoeGermuska]

now that I've run the installer, the "Knight Lab Data Visualization" page opens every time I open a VS Code project!

[graceeshao]

The extension was using onStartupFinished as its activation event, which fires in every VS Code window on startup. Now it only opens if the workspace contains the textbook folder. Let me know if this fixes the issue.