add AS Num for SHIP-11768 (#24635)

Author: ncrouch-cflare

src/content/docs/load-balancing/additional-options/load-balancing-rules/reference.mdx

@@ -120,6 +120,27 @@ Regardless of your traffic [proxy status](/load-balancing/understand-basics/prox
 				</p>
 			</td>
 		</tr>
+		<tr id="field-asnum">
+			<td valign="top">
+				<code>ip.src.asnum</code>
+				<br />
+				`Number`
+			</td>
+			<td>
+				<code>AS Number</code>
+			</td>
+			<td>
+				<p>
+					The 16-bit or 32-bit integer representing the Autonomous System (AS)
+					number associated with the client IP address.
+				</p>
+				<p>
+					Example value:
+					<br />
+					<code class="InlineCode">13335</code>
+				</p>
+			</td>
+		</tr>
 	</tbody>
 </table>