Add support of 'Customized built-in elements' to the CustomElementRegistry in Chromia BCD (and minor other tweaks) (#983)
Add support of 'Customized built-in elements' to the CustomElementRegistry in Chromia BCD (and minor other tweaks) (#983)

* making changes to the CustomElementRegistry BCD

* including customized built-in elements as a subfeature, as requested

mdn/browser-compat-data,teoli2003/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data