Update CONTRIBUTING.md to provide a more involved example of creating a command about command HOT 1 OPEN

Hi! Thanks for the feedback. I will work to improve the documentation with a more full-fledged example. In the meantime, here are some good places to start:

• Check out the implementation for the /giphy command here. Probably the biggest thing to see there is how we use the Container component (source here) to contain the search. This adds in all of the default UI you see in /giphy, /spotify, /emoji.
• Check out the Search component here. For the simplest implementation, you can use the Search.Widget component, which requires the props specified here. If you'd like to do something a little more involved, you can look to Emoji uses Search.Input and then does a custom rendering.

If you'd like to dive in, I can make myself available here to answer any questions you have getting set up!

from command.