Export Poetry's lockfile as pip requirements.txt

This will let the pre-commit hooks ensure
that Poetry's lockfile is kept up-to-date
and that it is exported to a pip `requirements.txt` file.

GitHub: fix mxcube#1268

.pre-commit-config.yaml

@@ -13,9 +13,19 @@ repos:
           - --strict
 
   - repo: https://github.com/python-poetry/poetry
-    rev: 1.5.0
+    rev: 1.8.3
     hooks:
       - id: poetry-check
+        args:
+          - --lock
+      - id: poetry-lock
+        args:
+          - --no-update
+
+  - repo: https://github.com/python-poetry/poetry-plugin-export
+    rev: 1.8.0
+    hooks:
+      - id: poetry-export
 
   - repo: https://github.com/myint/autoflake
     rev: v1.6.0