Ssh tunnel configuration for dsn aliases

[charbeljc]

Description

You can configure ssh tunnels for dsn aliases in your ~/.config/pgcli/config with

[dsn ssh tunnels]
^example_dsn$ = myuser:mypasswd@my.tunnel.com:4000

This takes precedence over host matches from [ssh tunnels] section.

Checklist

• I've added this contribution to the changelog.rst.
• I've added my name to the AUTHORS file (or it's already there).

• I installed pre-commit hooks (pip install pre-commit && pre-commit install).
• Please squash merge this pull request (uncheck if you'd like us to merge as multiple commits)