fix: Use manifest 'name' for 'short_name' if provided

[gabrielchl]

The current default manifest short_name is the project package name, even when a custom name is provided for the manifest. This is not ideal as developers might assume that when name is provided, short_name would default to be the same as name, especially that it's optional (https://developer.mozilla.org/en-US/docs/Web/Manifest/short_name).

This patch uses the name value (if provided) for short_name, and otherwise uses the project package name as usual.