Add zstd content-encoding

[vuolter]

Describe the feature

It would be great to have support for zstd compression (https://github.com/facebook/zstd). Browsers are now quite compatible with this content encoding (https://caniuse.com/zstd). Thank you

Additional information

• [X] Would you be willing to help implement this feature?
• [ ] Could this feature be implemented as a module?

Final checks

• [X] Check existing discussions and issues.