Improve history mode server configuration documentation to include non-root publicPath

[philBrown]

What problem does this feature solve?

The documentation for HTML5 History Mode - Example Server Configurations assumes all apps are running at the document root (ie /). Apps using a non-root publicPath are going to struggle with these config examples.

What does the proposed API look like?

Update the examples to include <publicPath> placeholders, eg

nginx

location <publicPath> {
  try_files $uri $uri/ <publicPath>/index.html;
}

[posva]

I think we can add a small paragraph at the beginning, before all examples, saying that they are targeting deployments at root / and then point out about the publicPath option in CLI and relate it to base in router options