### Feature and motivation

Adding parameter for subpath configuration so inside container application can work on different path than root.

I've tested rewrite rules on ingress and they do not work correctly.

### Usage example

Currently application works on http://localhost:4444 inside of the container, unfortunately in ingress implementation with reverse-proxy application will not respond correctly to ingress configuration where path is configured different than "/"
New parameter would allow to change base URL of the application to work on http://localhost/selenium:4444 which will allow correct communication with ingress.
public class RouterFlags implements HasRoles {
  @SuppressWarnings("FieldMayBeFinal")
  @Parameter(
    names = {"--relax-checks"},
    description = "Relax checks on origin header and content type of incoming requests," +
                  " in contravention of strict W3C spec compliance.",
    arity = 1)
  @ConfigValue(section = "network", name = "relax-checks", example = "true")
  private Boolean relaxChecks = false;
  @Parameter(
    names = "--username",
    description = "User name clients must use to connect to the server. " +
                  "Both this and password need to be set in order to be used.")
  @ConfigValue(section = "router", name = "username", example = "admin")
  private String username;
  @Parameter(
    names = "--password",
    description = "Password clients must use to connect to the server. " +
      "Both this and the username need to be set in order to be used.")
  @ConfigValue(section = "router", name = "password", example = "hunter2")
  private String password;
  @Override
  public Set<Role> getRoles() {
    return Collections.singleton(ROUTER_ROLE);
  }
}