Support .webmanifest static files.

[scottsauber]

Add support for static files with .webmanifest extensions which are commonly used for Progressive Web Apps - https://developer.mozilla.org/en-US/docs/Web/Manifest

Addresses #2442

[scottsauber]

@shirhatti - anything else you need from me on this?

[Tratcher]

FYI: https://github.com/aspnet/AspNetCore/blob/a9d3f9c22b16e16f017a36a6e8ae72902c2a698d/src/Middleware/StaticFiles/src/FileExtensionContentTypeProvider.cs#L14-L17

[scottsauber]

@Tratcher - ok so do you want me to just close this PR? No sense in leaving it open if there is no desire to merge it.

[huysentruitw]

@Tratcher @shirhatti this seems to be a problem for us when we enable a service worker in an Angular 8.2. Currently we need to use this work-around:

FileExtensionContentTypeProvider provider = new FileExtensionContentTypeProvider();
provider.Mappings[".webmanifest"] = "application/manifest+json";

app.UseStaticFiles(new StaticFileOptions
{
    ContentTypeProvider = provider,
});

Since more and more PWA's are being created, it seems a very logical step forward to be able to host this content type by default. It took us some time to figure this out.

For more information about this type, see https://www.w3.org/TR/appmanifest/

Thanks for reconsidering this.

[stephenlautier]

But why not support it if its still being used? Unless its obsolete, which doesnt seems like it - it will make our lives much easier by this small change

[huysentruitw]

Setting up a new project and here we are again... What do we miss to have this type in the framework? Do we need to create an official project template for PWA's?

When starting from the ASP.NET Core + Angular template, converting it to a PWA is as simple as executing ng add @angular/pwa --project ClientApp and then you're up for hours of googling why it doesn't work in your ASP.NET Core host until you come up at this issue... We can do better, right?