Tldr: Improve brew.md

[waldyrious]

From this comment by @MarloweW:

Maybe we could add brew info -f {{formula}}, it's useful to find out files contained in a formula.

We should also revise the list example, as discussed here, to get rid of the square brackets, which can be confusing. Ideally that could be done by rewording the description rather than splitting the example in two, since we're already at 6 examples and with the info -f we'd reach 7.

[wych42]

Since I commented that, I'll fire a PR for this.