Add 'fern deep' command to CLI reference documentation

This commit introduces a new CLI command 'fern deep' that allows users to send
emails directly to Deep, one of Fern's co-founders. The command includes options
for customizing the message and subject line, making it easy for users to provide
feedback, ask questions, or share ideas with the team.

Author: fern-support

fern/products/cli-api-reference/pages/commands.mdx

@@ -14,6 +14,7 @@ hideOnThisPage: true
 | [`fern logout`](#fern-logout) | Log out of the Fern CLI |
 | [`fern export`](#fern-export) | Export an OpenAPI spec for your API |
 | [`fern api update`](#fern-api-update) | Manually update your OpenAPI spec |
+| [`fern deep`](#fern-deep) | Send an email to Deep, our co-founder |
 
 ## Documentation commands
 
@@ -587,4 +588,51 @@ hideOnThisPage: true
     ```
   </CodeBlock>
   </Accordion>
+
+  <Accordion title="fern deep">
+
+    Use `fern deep` to send an email directly to Deep, one of our co-founders. Whether you have feedback, questions, or just want to say hi, Deep is always happy to hear from the community!
+
+    <CodeBlock title="terminal">
+    ```bash
+    fern deep [--message <your-message>] [--subject <subject>]
+    ```
+    </CodeBlock>
+
+    When run without options, this command will open your default email client with a pre-addressed message to Deep.
+
+    ### message
+
+    Use `--message` to include a specific message in your email.
+
+    ```bash
+    fern deep --message "Love the new SDK generation features!"
+    ```
+
+    ### subject
+
+    Use `--subject` to set a custom subject line for your email.
+
+    ```bash
+    fern deep --subject "Feature Request: GraphQL Support"
+    ```
+
+    ### Example usage
+
+    ```bash
+    # Open email client
+    fern deep
+
+    # Send a quick message
+    fern deep --message "Thanks for building Fern!"
+
+    # Send detailed feedback
+    fern deep --subject "Feedback on TypeScript SDK" --message "The generated types are excellent!"
+    ```
+
+    <Tip>
+    Deep loves hearing from users! Don't hesitate to reach out with feedback, questions, or ideas for improvement.
+    </Tip>
+
+  </Accordion>
 </AccordionGroup>