Read config values via CLI selectively

[NobbZ]

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?

[kytrinyx]

I like this idea -- it's very clean!