Add links to more scanner docs for offline support

What does this MR do?

Adds links to the offline environment docs for Secret Detection and API Fuzzing.

It's possible there is a better way to document this for API Fuzzing since the API Fuzzing doc just links back to this main Offline environments doc. I started with this since it does help make it more discoverable that API Fuzzing is supported for offline environments.

Note: I don't understand the order that the analyzers are listed in this section, but didn't change it to keep the diff smaller.

Related issues

No related issue. This came up in a Slack conversation.

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