Rename extension name to quasar-app-extension-ssg

[IlCallo]

Same reason behind #7, static is a very generic word too.
quasar ext add static is a bit generic, quasar ext add ssg is already clearer

The AE name is expecially important because once a package is added to NPM I think it's impossible to remove it, you can just deprecate it, and littering the registry with duplicates would cause confusion in the ecosystem

[freddy38510]

Fixed in f6f9bea