add semantic markup to docs

[evgeni]

SUMMARY

• [Associated vote ended on 2023-03-09] Include semantic markup in plugin DOCUMENTATION strings ansible-community/community-topics#53
• ansible-doc: add semantic markup support ansible/ansible#80242
• Add new semantic markup support ansible-community/antsibull-docs#4

As this feature is not being backported to older Ansible releases, the ansible-doc output there would become "ugly".
We probably should wait before we actually implement that.

ISSUE TYPE

• Feature Idea