Activate extension on vscode startup via setting or globally.

[Confectrician]

I think the need of opening an openHAB related file can be confusing.
Especially when one uses vscode mainly for openHAB configuration.

My idea is to start the extension on vscode startup, but provide a setting which prevents this behavior of one doesn't want it to be started directly.

Reference:
https://code.visualstudio.com/api/references/activation-events#Start-up

[Confectrician]

Maybe the better solution:
https://code.visualstudio.com/api/references/activation-events#workspaceContains

Check for typical openhab folder structures and files and activate the extension immediately.
No setting needed.

[Confectrician]

This would also be needed for the discussed jsr support in #141