Document the certificate chain cache

## Why

We want to document the certificate chain cache mechanism in the documentation website.

## What

Document the certificate chain caching (and the different modes) as well as security impact.

## How

- [ ] Update the client documentation
- [ ] Update the client CLI documentation
- [ ] Update the examples to showcase the certificate chain cache
- [ ] Update the certificate chain page of the website
- [ ] Create a dev blog post to announce the availability of the cache

Start by locating the client documentation, client CLI documentation, examples, certificate chain page, and dev blog areas mentioned in the checklist. Read the existing certificate-chain material first, then document caching, its different modes, and security impact across those locations. Done means all five checklist items are addressed.

Written by the indexing model from the issue text.