Improve of monorepo support

[tom-wegener]

We use a monorepo approach to develope some applications where we have the backend and frontend in one repository but in different folders like in the 'big projects' example from the biomejs documentation.

Most of the time we open the whole repository in vscode but the extension cannot find the config file (except when we add one in the root which just points to the one in the right folder) or the executable in the node_modules folder since both are not in the root directory.

I think a better resolution than just looking into the root directory which also goes into some directories would improve the UX.

The prettier extension could be used as an example since our setup works with prettier at the moment.