Clarify component paths and directory structure

What does this MR do and why?

This MR is extracted from feedback in https://gitlab.com/gitlab-com/marketing/developer-relations/dev-evangelism/de-tmm-meta/-/issues/230#note_1627077632

Clarify component paths and directory structure:

• Replace my-component with my-project to indicate that the given token in the path represents a project.
• Rephrase how the directory structure works for more complex use case.

Changelog: other

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