feat(popup): support dark mode

A new CSS is used to support dark mode.

Author: Linkid

popup/popup.css

@@ -0,0 +1,13 @@
+:root {
+  --bg: #fff; --fg: #1b1b1b; --muted: #6b6b6b;
+  --link: #0060df; --border: #e0e0e0;
+}
+@media (prefers-color-scheme: dark) {
+  :root { --bg: #1c1b22; --fg: #fbfbfe; --muted: #b1b1bd;
+          --link: #80b3ff; --border: #38383d; }
+}
+
+.popup { background: var(--bg); color: var(--fg); }
+.pr-list a { color: var(--link); text-decoration: none; }
+.pr-list a:hover { text-decoration: underline; }
+.pr-list__empty, .pr-list__loading, #error { color: var(--muted); }

popup/popup.html

@@ -4,6 +4,7 @@
   <head>
     <meta charset="utf-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <link rel="stylesheet" href="popup.css">
   </head>
 
   <body>