docs for secret cache (dapr/dapr#3941)

[Taction]

What content needs to be created or modified?

Add cacheEnable cacheTTL cacheMemoryLimit cache config metadata. Add refresh_cache metadata in request.

Describe the solution you'd like

Where should the new material be placed?

The associated pull request from dapr/dapr, dapr/components-contrib, or other Dapr code repos

Specify the URL to the associated pull request, if applicable

https://github.com/dapr/dapr/pull/3941

Additional context