ci: cache pre-commit environment

.gitlab-ci.yml

@@ -39,6 +39,8 @@ Check licenses:
   interruptible: true
 
 Check style:
+  variables:
+    PRE_COMMIT_HOME: ${CI_PROJECT_DIR}/pre-commit
   before_script:
     - apk add git pre-commit
   script:
@@ -50,6 +52,12 @@ Check style:
       when: manual
     - when: always
   interruptible: true
+  cache:
+    key:
+      files:
+        - .pre-commit-config.yaml
+    paths:
+      - ${PRE_COMMIT_HOME}
 
 include:
   - project: "anw_dienste/ci-templates"