prevent caching of embeddable

[ignatandrei]

For each map points where
app.Run(async context =>

add the following code:

context.Response.OnStarting(() =>
{

                    if (!context.Response.Headers.ContainsKey("Cache-Control"))
                    {
                        context.Response.Headers.Add("Cache-Control", "no-cache, no-store");
                    }

                    return Task.CompletedTask;
                });