Add caching to build pipeline

.drone.yml

@@ -5,11 +5,33 @@ type: docker
 name: default
 
 steps:
+  - name: restore cache
+    image: meltwater/drone-cache
+    environment: &cache_env
+      SFTP_HOST: u194355-sub5.your-storagebox.de
+      SFTP_PORT: '23'
+    settings:
+      <<: &cache_settings
+        backend: sftp
+        mount:
+          - resources/_gen
+        public_key_file:
+          from_secret: cache_ssh_key
+        username: u194355-sub5
+      restore: yes
+
   - name: build
     image: klakegg/hugo:ext-alpine-ci
     commands:
       - hugo --baseURL="https://staging.www.kontakt-bamberg.de/"
 
+  - name: rebuild cache
+    image: meltwater/drone-cache
+    environment: *cache_env
+    settings:
+      <<: *cache_settings
+      rebuild: yes
+
   - name: deploy
     image: appleboy/drone-scp
     settings: