opus and webp for modern browsers

[jnorthrup]

i touched on this in #28 breifly, these two codec formats are doing arithmetic lossless compression nearly to shannon's limit and the general ffmpeg conversion framework is in #28 as well to add a third audio for opus, and to potentially centralize the image asset conversion step identically with ffmpeg.

how gwt 3+ makes the determination for which image formats in which browser to use is something I claim to be of no help, and truth be told noone would actually notice webp load times given that the cpu needs increase as the bandwidth needs decrease.

but someone has to mention it for 99/100 lighthouse scores. right?