Read config values via CLI selectively

When we want to debug settings we always ask for the output of `exercism configure` with the hint to redact/remove the token from the ouptut.

So this time, I was only interested in the API URL, so I asked for the output of `exercism configure 2>&1 | grep -- --all` this feels very clumsy.

Can we have an interface like with `git config` where `git config foo` reads and `git config foo bar` writes?