Report Failure to create WebGL context, or low FPS

[cdiggins]

A pop-up saying when the WebGL context can't be created of the FPS is too low (e.g. below 8FPS) should show on load, saying what the graphics card is, and providing them with a clue that maybe they need to enable hardware acceleration for their browser to get the best experience. Some GPU info can be gathered with this code: https://gist.github.com/cvan/042b2448fcecefafbb6a91469484cdf8

[cdiggins]

Failure to created WebGL context could be exposed to the user (host environment) as an "onError" callback in the options. Would need an API to request the FPS from the viewer. This is all arguably a feature request and more appropriate for the vim-webgl-app.