load css seperately

manifest.json

@@ -4,17 +4,15 @@
     "description": "The most popular dark theme extension for github",
     "manifest_version": 2,
     "icons": { 
-        "16": "assets/icon.png",
-        "48": "assets/icon.png",
-        "128": "assets/icon.png"
+        "16": "assets/icon3.png",
+        "48": "assets/icon2.png",
+        "128": "assets/icon1.png"
     },
     "content_scripts" : [
         {
             "matches": ["https://github.com/*"],
-            "js": [
-                "jquery.js",
-                "content.js"
-            ]
+            "css": ["src/style.css"],
+            "js": ["src/content.js"]
         }
     ]
 }

src/content.js

@@ -0,0 +1,36 @@
+function ready(eventHandler) {
+    if (document.readyState !== 'loading') {
+        eventHandler();
+    } else {
+        document.addEventListener('DOMContentLoaded', eventHandler);
+    }
+}
+
+ready(function() {
+    const dayElements = document.getElementsByClassName('day');
+    if (dayElements.length == 0) return;
+
+    for (const dayEl of dayElements) {
+        if (dayEl.getAttribute("fill") == "#ebedf0") {
+            dayEl.setAttribute("fill", "#272c32");
+        }
+        if (dayEl.getAttribute("fill") == "#c6e48b"){
+            dayEl.setAttribute("fill", "#1d2125")
+        }
+        if (dayEl.getAttribute("fill") == "#7bc96f"){
+            dayEl.setAttribute("fill", "#131619")
+        }
+        if (dayEl.getAttribute("fill") == "#239a3b"){
+            dayEl.setAttribute("fill", "#090b0c")
+        }
+        if (dayEl.getAttribute("fill") == "#196127"){
+            dayEl.setAttribute("fill", "#000")
+        }
+    }
+
+    document.querySelector(".legend > li:nth-child(1)").setAttribute("style", "background-color:#272c32");
+    document.querySelector(".legend > li:nth-child(2)").setAttribute("style", "background-color:#1d2125");
+    document.querySelector(".legend > li:nth-child(3)").setAttribute("style", "background-color:#131619");
+    document.querySelector(".legend > li:nth-child(4)").setAttribute("style", "background-color:#090b0c");
+    document.querySelector(".legend > li:nth-child(5)").setAttribute("style", "background-color:#000");
+});