dbt CLI: Improve your terminal experience page

[infused-kim]

Hello everyone,

People using dbt CLI spend A LOT of time in the terminal running dbt commands. So I think it would make a lot of sense to add a new section to the dbt CLI documentation that says something like "Improve your terminal experience".

In there we can point people towards how to set up dbt shell completions:
https://github.com/dbt-labs/dbt-completion.bash

And perhaps fzf-dbt, which adds an interactive dbt model search and selection. It has completely changed how I use dbt:
https://github.com/Infused-Insight/fzf-dbt

Let me know what you think.

If you like the idea, I would be happy to draft something up and submit a PR.