Merged 4.0 into main

no issue

- Casper is now ready for 4.0 so this commit merges the branch in to try
  and keep the Git history as clean as possible

package.json

@@ -2,10 +2,10 @@
     "name": "casper",
     "description": "A clean, minimal default theme for the Ghost publishing platform",
     "demo": "https://demo.ghost.io",
-    "version": "3.1.3",
+    "version": "4.0.0-rc.0",
     "engines": {
-        "ghost": ">=3.0.0",
-        "ghost-api": "v3"
+        "ghost": ">=4.0.0",
+        "ghost-api": "v4"
     },
     "license": "MIT",
     "screenshots": {
@@ -88,5 +88,10 @@
                 "width": 2000
             }
         }
+    },
+    "renovate": {
+        "extends": [
+            "@tryghost:theme"
+        ]
     }
 }