[resource-hints] first spec draft

First run at the spec based on previous discussions [1] and feedback:
https://igrigorik.github.io/resource-hints/

*"This specification defines preconnect, preload, prefetch, and prerender
hints that the developer, or the server generating or delivering the
resources, can use in an interoperable way to assist the user agent in the
decision process of which origins it should connect to, which resources it
should fetch to improve performance, and which resources may be required by
the next navigation."*

Feedback, nitpicks, etc., all welcome!

ig

[1]
https://docs.google.com/document/d/1HeTVglnZHD_mGSaID1gUZPqLAa1lXWObV-Zkx6q_HF4/edit#