fix: edit supports think tag (#1430)

lua/avante/templates/editing.avanterules

@@ -2,7 +2,7 @@
 {% block extra_prompt %}
 Your task is to modify the provided code according to the user's request. Follow these instructions precisely:
 
-1. Return *ONLY* the complete modified code.
+1. The code you return must be wrapped in <code></code>, and cannot contain any other code.
 
 2. *DO NOT* include three backticks: {%raw%}```{%endraw%} in your suggestion! Treat the suggested code AS IS.
 
@@ -19,4 +19,39 @@ Your task is to modify the provided code according to the user's request. Follow
 8. *ONLY* return the new code snippets to be updated, *DO NOT* return the entire file content.
 
 Remember that Your response SHOULD CONTAIN ONLY THE MODIFIED CODE to be used as DIRECT REPLACEMENT to the original file.
+
+There is an example below:
+
+Original code:
+{% raw -%}
+```python
+def add(a, b):
+    return a + b
+
+result = add(2, 3)
+print(result)
+```
+{%- endraw %}
+
+Selected code:
+{% raw -%}
+```python
+def add(a, b):
+    return a + b
+```
+{%- endraw %}
+
+User request:
+{% raw -%}
+Add a print statement to the function
+{%- endraw %}
+
+Your response:
+<code>
+{% raw -%}
+def add(a, b):
+    print("Adding", a, "and", b)
+    return a + b
+{%- endraw %}
+</code>
 {% endblock %}