Prepare for implementation report

[himorin]

While CR phase, WG/editors need to prepare an implementation report to show adequate implementation experience, to go further like PR and REC. Normally, browser related specs rely on wpt, and WebXR Device API could follow that using webxr test results in wpt.

So, preparation tasks would be like:

• pick which tests are relevant to WebXR Device API spec
• check whether picked tests covers every normative items in the spec
• if any other implementation could be used for implementation report, like software on XR devices without chromium, need to perform tests and show results

/facetoface