Add pre-commit hook.

.pre-commit-config.yaml

@@ -0,0 +1,10 @@
+repos:
+  - repo: https://github.com/psf/black
+    rev: 24.8.0
+    hooks:
+      - id: black
+        name: Format Python code with black
+        entry: black
+        args: ["knowledge_storm/"]
+        language: python
+        pass_filenames: true

CONTRIBUTING.md

@@ -40,9 +40,9 @@ Following the suggested format can lead to a faster review process.
 
 **Code Format:**
 
-We adopt [`black`](https://github.com/psf/black) for arranging and formatting Python code. Please complete the following step before submitting the PR. See [here](https://github.com/psf/black?tab=readme-ov-file#installation-and-usage) for more information.
-```shell
-pip install black
-black {path_to_the_changed_python_code}
+We adopt [`black`](https://github.com/psf/black) for arranging and formatting Python code. To streamline the contribution process, we set up a [pre-commit hook](https://pre-commit.com/) to format the code under `knowledge_storm/` before committing. To install the pre-commit hook, run:
 ```
-
+pip install pre-commit
+pre-commit install
+```
+The hook will automatically format the code before each commit.