Add wasm bindings for buffer_ranges_function

[glalonde]

I definitely messed up my fork with rebases, but the commits are all the same.

I'm not sure why spirv_cross msl/hlsl aren't working, but it seems someone disabled them in #111, maybe with good reason. So I changed the wasm CI script to only run the glsl example for that target(is that the only dialect that will run via javascript?).

[glalonde]

The build passes: https://travis-ci.com/glalonde/spirv_cross/builds/147020797

[glalonde]

If you'd prefer not to install emcc, I can do these steps after merging this PR.

sgtm, I'm not sure how to do that.

[grovesNL]

Ok sounds good

(If you're ever interested for some reason, the Emscripten SDK installation guide is located at https://emscripten.org/docs/getting_started/downloads.html)

bors r+

[bors[bot]]

Build succeeded

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