Add implicit request mapping to `@Head` when the service is mapped to `@Get`

Many server frameworks(e.g. Spring, express) create an implicit request mapping to HEAD when there’s a request handler for GET.

The feature can be useful as client sometimes just want to check the existence of resources without receiving the whole body and almost always the handlers for @Get and @Head should be the same.

Currently, armeria needs 3 annotations to do the same thing.

@Get
@Head
@Path("/some-file")
public HttpResponse someFile(ServiceRequestContext ctx) {
    // ...
    return client.execute(RequestHeaders.of(ctx.method(), "/some-object-storage-path"));
}

[ks-yim]

@Parkkibum95 Thanks, it seems no one has started working on this 😆

[Parkkibum95]

may i try this? 🚀