CI: configure dependabot to bump Python deps (deepmodeling#5072)

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## Summary by CodeRabbit

* **Chores**
  * Improved dependency management automation for Python packages.

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Signed-off-by: Jinzhe Zeng <jinzhe.zeng@ustc.edu.cn>

Author: njzjz

.github/dependabot.yml

@@ -5,3 +5,8 @@ updates:
     schedule:
       interval: "weekly"
     target-branch: "devel"
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    target-branch: "devel"