Unify the steps about creating pleroma user home directory in the docs
When I tried to have my pleroma instance migrate from source build version to OTP releases-based installation, docs caused me confusing about pleroma user home directory settings.
In Installing on Debian Based Distributions, doc says
sudo useradd -r -s /bin/false -m -d /var/lib/pleroma -U pleroma to create a user. I installed pleroma with this method before.
So I had to change pleroma user home directory by
usermod -d /opt/pleroma pleroma while migrating the pleroma installation.
Would you mind considering the unified approach to this home directory settings between docs?