now at proof of concept stage(thanks He4eT!)

manifest.json

@@ -15,11 +15,8 @@
     },
     "content_scripts": [
         {
-            "js": ["scripts/content.js"],
+            "js": ["scripts/milje.js"],
-            "matches": [
+            "matches": ["<all_urls>", "file:///"]
-                "https://developer.chrome.com/docs/extensions/*",
-                "https://developer.chrome.com/docs/webstore/*"
-            ]
         }
     ]
 }

milje.js

@@ -1 +0,0 @@
-console.log("this is where the milje code goes somehow...")