Review analysis/overview.md after new pages were created on developer.yoast.com

[hdvos]

Please give us a description of the issue

• I've read and understood the contribution guidelines.
• I've searched for any related issues and avoided creating a duplicate issue.

This task was created as part of this task: https://github.com/Yoast/non-dev-tasks/issues/39
See report in first comment to this task for context.

This task is blocked by:

• Add documentation for Free and Premium assessments to developer.yoast.com #226
• Create documentation on Supported Content types on developer.yoast.com #227
• Create documentation for supported editors on developer.yoast.com #228

In these three tasks, documentation was added to developer.yoast.com. As a result analysis/overview.md might have information that is redundant now, or could better live in the newly created pages.

• Review analysis/overview.md to assess which information could be removed or replaced.
• Add links to the overview pages created in Add documentation for Free and Premium assessments to developer.yoast.com #226, Create documentation on Supported Content types on developer.yoast.com #227 and Create documentation for supported editors on developer.yoast.com #228