Dev add docs

[trickMin]

Description

• add response-header-rewrite plugin docs

• add static-downgrade plugin docs

Affects

To help us figure out who should review this PR, please put an X in all the areas that this PR affects.

• [ ] Configuration Infrastructure
• [x] Docs
• [ ] Installation
• [ ] Performance and Scalability
• [ ] Test and Release
• [ ] User Experience