Use --project=@. by default (again?)

[goerz]

It seems like when I run IJulia.installkernel("Julia"), the resulting kernel no longer has "--project=@.". It was the default in
v1.18, introduced in #820. I'm not seeing any release notes to indicate when the default changed.

There's #928 about this. For the record, I strongly prefer the --project=@. behavior as a default. In any case, the issue is still open, and without the change being in a changelog, this seems like a "bug".

Can we go back to the old behavior, pretty please? ;-)

[goerz]

Or, at the very least, can we have a very prominent note in the README and the docs that explains the situation and recommends running

IJulia.installkernel("Julia", "--project=@.")

for those who like the behavior