Rely only on properties object to get/set properties

Investigate if we can get rid of the Document#get and Document#set methods to only rely on the properties object directly.

The main issue is to check if we can extract the dirty properties when updating the properties object.

See if we can rely on https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy

If it works, deprecate the old get/set methods and update the documentation.