Create an empty default welcome file

[pljones]

Originally posted by @ann0see in #3194 (review)

I'd not do it this way.
Modify the files in this folder instead: https://github.com/jamulussoftware/jamulus/tree/main/linux/debian
Add an empty .html file to the directory.

Add the empty file here: https://github.com/jamulussoftware/jamulus/blob/main/linux/debian/jamulus.install and here: https://github.com/jamulussoftware/jamulus/blob/main/linux/debian/jamulus-headless.install

Maybe you'd also need to edit https://github.com/jamulussoftware/jamulus/blob/main/linux/deploy_deb.sh