docs: Subagents (#3402)

Co-authored-by: angiejones <jones.angie@gmail.com>

documentation/docs/experimental/index.md

@@ -19,6 +19,11 @@ The list of experimental features may change as Goose development progresses. So
 <div className={styles.categorySection}>
   <h2 className={styles.categoryTitle}>🧪 Experimental Features</h2>
   <div className={styles.cardGrid}>
+      <Card 
+      title="Subagents"
+      description="Independent instances that execute tasks while keeping your main conversation clean and focused. Run tasks sequentially or in parallel with process isolation and context preservation."
+      link="/docs/experimental/subagents"
+    />
     <Card 
       title="Ollama Tool Shim"
       description="Enable tool calling capabilities for language models that don't natively support tool calling (like DeepSeek) using an experimental local interpreter model setup."