Add Godrays PR as a WebGL 2 only example

Hello, as the Godrays posteffect currently isn't available (anyway; as you write it needs to be compatible with WebGL 2.0), I want to hear if it can become so anyway in here as a github-source? (at least temporarely)

Even though I bought GodRays from Leonidas/Pirron-One, he did not reply with an answer a link from himself (he made available for our community some years ago).

Actually I would argue that it should be available in any case, as it (the WebGL 2.0-benchmark) is already above 80% penetration (https://www.khronos.org/blog/webgl-2-achieves-pervasive-support-from-all-major-web-browsers).

Testing of '1.0 or 2.0' should also be manageable according to: https://stackoverflow.com/questions/51428435/how-to-determine-webgl-and-glsl-version
Developers would then have the option of writing this to the user "This app's post effects is only supported by WebGL 2.0, which your device does comply to".

PS: I now there are Contributing Guidelines, but could not find a suit for this kind of issues.

Start by reviewing the repository's contributing guidelines and the existing examples structure; no specific file or test is named in the issue. Verify whether the Godrays source can be included, then determine how a WebGL 2-only example should be exposed and tested. Done should mean an approved, usable example with clear WebGL 2 compatibility guidance.