Fix favicon (#844)

This PR fixes the missing facicon.
As part of the migration to vite, this issue was introduced.
- #836

index.html

@@ -5,6 +5,7 @@
   <title>Maputnik</title>
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <link rel="manifest" href="src/manifest.json">
+  <link rel="icon" href="src/favicon.ico" type="image/x-icon" />
   <style>
     html {
       background-color: rgb(28, 31, 36);