Add quickstart doc for bundle authors

[VinozzZ]

Currently, porter's quickstart focuses more on how to run a bundle using Porter. We would like to add some helpful quickstart guide for bundle authors as well.
We have one existing doc to make a bundle https://getporter.org/bundle/create/ and another doc page that explains all the bundle values that can be changed https://getporter.org/bundle/manifest/

We can break down some of the common settings that bundle authors can change in porter.yaml and group them together and add a few more quickstart docs on those concepts

[VinozzZ]

#1980

[carolynvs]

@VinozzZ I don't quite get why you linked #1980? I'm sure it makes sense but my brain is failing me! 😂