Add Support for automatic conversion to WebP Image format

[dellis1972]

There is a new tool to optimise images into a webp format. This seems to produce at 26% reduction in size on png image, 23-24% on jpg. They do provide a command line tool, so we could introduce an option to auto convert the images when we build our apps.
Alternatively, provide a UI within the IDE's to allow users to convert their images from within the IDE.

[jpobst]

In general, these types of tools can take 20-60s to optimize an image, so doing it automatically during the build probably isn't a good idea. One possibility would be to work with Mads to add it to https://marketplace.visualstudio.com/items?itemName=MadsKristensen.ImageOptimizer, and try to push people towards that (which also supports many other image optimizations).

[JonDouglas]

@dellis1972 Seems like we will need to ship a precompiled library?

https://developers.google.com/speed/webp/docs/precompiled

Generally speaking, I don't see it being a super difficult thing to add into Visual Studio. Especially if we shipped a default quality:

https://developers.google.com/speed/webp/docs/using

@jpobst Brings up a good point, which is what if this extension already has equivalent optimization to webp? Although I wasn't able to find much on this, this article suggests that Zopfli does not perform as well as webp at higher file sizes / resolutions.

https://www.ctrl.blog/entry/webp-vs-guetzli-zopfli.html

It does seem ideal for an extension like ImageOptimizer to add webp support. However, I think we should keep an eye on including this into our workload by default as well.

Aside: I wonder if it makes sense to potentially make a open source repo of extensions for Android helpers?