inject webmanifest also at dev mode

Is it possible to inject the webmanifest not only at build, but at `astro dev`? Looked briefly into the integration API and it seems that  there is no hook present that we "just can use" to replicate the behavior for dev, too.

Maybe the injection via script at `astro:config:setup` is possible - if injected webmanifest elements after page load will be applied?