Hide the host until all Light or Shadow DOM blocking links are loaded,
Hide the host until all Light or Shadow DOM blocking links are loaded,

https://github.com/Starcounter/starcounter-include/issues/93

Support light and Shadow DOM,
opt-out capabilities with `async` attribute,
Cover race condition between resources load and changing composition or content,
Prepare for default custom-element styles Web Platform feature

Starcounter/starcounter-include,Starcounter/starcounter-include