The loading page is constructed on web/index.html.
<body >
<h1 style="color:black; font-family: Arial, Helvetica, sans-serif;">
loading site
</h1>
<img src="assets/images/oppkey_logo.jpg">flutter build web --base-href=/oppsite/
In ./build/web/, copy all files in ./docs/
Push up to GitHub.
At the moment, there is a problem with the assets/ folder. You must
manually move the assets up one level to avoid assets/assets.