Devfile how-to documentation

[rtaniwa]

Problem:
Right now, we are missing a guided How-to for how to author a devfile.

Goal:
Provide a how-to documentation which walk a reader (and developer) into each of the steps that are needed in order to get a devfile for from a simple project, to something a bit more advanced.

We need to look at different scenarios (not exhaustive):

• My source code exist, how do I get started?
  • From existing stack's devfile
  • What if there is not a suitable devfile for my project
• How to add different services
  • Database
  • Tools
  • New component
• How to configure it for Build, Run and Debug?
• Speak about the tools that can use devfile.

Why is it important?
This How-tos should help users and customers to get start with devfile. They should learn how they can create the devfile for their own project. Today, devfile are mostly used for getting started and we want more project leveraging it (along with the tools that can leverage it)

[Jdubrick]

I believe a combination of docs from https://devfile.io/docs/2.2.2/authoring-overview and https://devfile.io/docs/2.2.2/adding-components could be used to achieve a how-to instruction.