Add missing colon

[mikelolasagasti]

This errors are being silently ignored by go-yaml.

Example, without colon:

$ grep ^tags /home/user/.config/cheat/cheatsheets/community/kitty
tags [ kitty ]

$ cheat -t kitty
$

Adding missing colon:

$ grep ^tags /home/user/.config/cheat/cheatsheets/community/kitty
tags: [ kitty ]

$ cheat -t kitty
title: file:                                                 tags:
kitty  /home/user/.config/cheat/cheatsheets/community/kitty community,kitty

[chrisallenlane]

Oh, this is a great catch. Thanks very much.

I'm planning to eventually implement some sort of linter for cheatsheet content, but haven't had the time. This would be a good defect to scan for.