Force Clever Cloud to install requirements before building

.clever.json

@@ -0,0 +1,9 @@
+{
+  "apps": [{
+    "app_id": "app_3fc71684-b54a-480c-a511-76b8607a9a8d",
+    "build": {
+      "type": "static",
+      "cmd": "pip install -r requirements.txt && mkdocs build --site-dir cc_static_autobuilt"
+    }
+  }]
+}