Add instructions to consume other file formats that are not directly supported by devfile

[elsony]

/area documentation

Which area this documentation change is related to?
/area api

Issue details

What mistake did you find / what is missing in the documentation?
Add instructions to exec other tools or consume other file formats that are not directly supported by devfile. There are many other configuration files or systems that an existing customer may be using, e.g. helm, tilt, dev container, etc. The devfile specification may not have a native way to include those configuration files as part of the devfile (similar to kubernetes yaml in the kubernetes component or dockerfile in the image component).

However, the user will still be able to execute those when running the devfile by:

1. creating their own container to contain the tools requires to run those configuration files
2. create an exec command to run those configuration files within the container

This instruction will walk-through an example to help user to understand how to consume other configuration files in a devfile.

[thepetk]

This is a nice item. I've added it as a devtools week item.

[github-actions]

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