Add --jack flag to CLI reference for emailing Jack

Added documentation for the --jack flag that allows users to send emails
directly to Jack, one of Fern's co-founders. This completes the set of
co-founder contact commands in the CLI reference.

Changes include:
- Added --jack to the main commands table
- Created comprehensive accordion documentation section
- Documented all three options: --message, --subject, and --respond_to
- Provided usage examples showing individual option usage and combined usage
- Added helpful tip encouraging users to reach out

The CLI reference now supports contacting all three co-founders individually
(--dsinghvi, --dsheridan, --jack) or both Deep and Danny together (--fernie).

Author: fern-support

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

@@ -17,6 +17,7 @@ hideOnThisPage: true
 | [`fern --dsinghvi`](#fern---dsinghvi) | Send an email to Deep, our co-founder |
 | [`fern --dsheridan`](#fern---dsheridan) | Send an email to Danny, our co-founder |
 | [`fern --fernie`](#fern---fernie) | Send an email to both co-founders |
+| [`fern --jack`](#fern---jack) | Send an email to Jack, our co-founder |
 
 ## Documentation commands
 
@@ -755,4 +756,59 @@ hideOnThisPage: true
     </Tip>
 
   </Accordion>
+
+  <Accordion title="fern --jack">
+
+    Use `fern --jack` to send an email directly to Jack, one of our co-founders. Whether you have feedback, questions, or just want to say hi, Jack is always happy to hear from the community!
+
+    <CodeBlock title="terminal">
+    ```bash
+    fern --jack [--message <your-message>] [--subject <subject>] [--respond_to <email>]
+    ```
+    </CodeBlock>
+
+    When run without options, this command will open your default email client with a pre-addressed message to Jack.
+
+    ### message
+
+    Use `--message` to include a specific message in your email.
+
+    ```bash
+    fern --jack --message "Love the new SDK generation features!"
+    ```
+
+    ### subject
+
+    Use `--subject` to set a custom subject line for your email.
+
+    ```bash
+    fern --jack --subject "Feature Request: GraphQL Support"
+    ```
+
+    ### respond_to
+
+    Use `--respond_to` to provide your email address so Jack can respond to you.
+
+    ```bash
+    fern --jack --respond_to "[email protected]"
+    ```
+
+    ### Example usage
+
+    ```bash
+    # Open email client
+    fern --jack
+
+    # Send a quick message
+    fern --jack --message "Thanks for building Fern!" --respond_to "[email protected]"
+
+    # Send detailed feedback with all options
+    fern --jack --subject "Feedback on TypeScript SDK" --message "The generated types are excellent!" --respond_to "[email protected]"
+    ```
+
+    <Tip>
+    Jack loves hearing from users! Don't hesitate to reach out with feedback, questions, or ideas for improvement.
+    </Tip>
+
+  </Accordion>
 </AccordionGroup>