Fix: install rsync in drone.yml

.drone.yml

@@ -0,0 +1,21 @@
+kind: pipeline
+name: StaticWebsite
+type: docker
+
+steps:
+  - name: Deploy
+    image: python:3.8-alpine
+    commands:
+      - pip install --no-cache-dir -r requirements.txt
+      - pelican ./content/ -o ouptut -s publishconf.py --relative-urls
+      - apk apk add --no-cache openssh-client ca-certificates bash
+      - apk apk add rsync
+      - eval `ssh-agent -s`
+      - echo "$SSH_KEY" | ssh-add -
+      - mkdir -p ~/.ssh
+      - echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config
+      - rsync -rv --exclude ".git/" --delete -e "ssh -p 22" ./ sshcontent@91.121.90.228:~/raw.opytex.org/www/ --checksum
+    environment:
+      SSH_KEY:
+        from_secret: sshcontent-key
+