Reorganize "Add a Component docs"

[kim-tsao]

/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?

The Adding a component doc and subtopics should be re-organized to include the description of fields relevant to each sub-topic. See comment devfile/docs#147 (review)

[thepetk]

closing as rotten (created > 2 years). Feel free to re-open if you think is still a requirement.