feat(templates): avanterules filetype support (closes #254) (#466)

Signed-off-by: Aaron Pham <contact@aarnphm.xyz>

lua/avante/templates/editing.avanterules

@@ -0,0 +1,22 @@
+{% extends "planning.avanterules" %}
+{% block user_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.
+
+2. Do not include any explanations, comments, or line numbers in your response.
+
+3. Ensure the returned code is complete and can be directly used as a replacement for the original code.
+
+4. Preserve the original structure, indentation, and formatting of the code as much as possible.
+
+5. Do not omit any parts of the code, even if they are unchanged.
+
+6. Maintain the SAME indentation in the returned code as in the source code
+
+7. DO NOT include three backticks: {%raw%}```{%endraw%} in your suggestion. Treat the suggested code AS IS.
+
+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.
+{% endblock %}