[FR]: XDG base directory support

[Samq64]

Description

Store the NSS configuration in $XDG_DATA_HOME/pki instead of $HOME/.pki

Who's implementing?

• I'm willing to implement this feature myself

The problem

It can be annoying to have an extra directory in the $HOME that doesn't need to be there.

Possible solutions

Use ~/.pki if it already exists, otherwise create it under $XDG_DATA_HOME/pki insead of the home directory.

Additional context

ungoogled-chromum issue: ungoogled-software/ungoogled-chromium#2255
Chromium issue: https://issues.chromium.org/issues/40666379

Moving the cahce out of .config would also be nice but much more work and probably not worth it.