Resolve "Update docs for new SSE config file"

What does this MR do?

Problem to solve

• Adds documentation for new Static Site Editor config file and entries, introduced as part of &4267 (closed)
• Also clarifies documentation around existing Static Site Generator data/config.yml config file: #247841 (closed)
• Links to docs updated:
  • http://docs-preview-ee-44507.178.62.207.141.nip.io/ee/user/project/static_site_editor/

Further details

Does this MR meet the acceptance criteria?

Conformity

• Documentation (if required)
• Code review guidelines
• Style guides

Other links/references

• Issue: Related to #262844 (closed)
• Epic with issues to be documented: &4267 (closed)