Should throw an error when given invalid framebuffer properties

[rreusser]

regl.framebuffer({foo: 'bar'}) doesn't throw an error about invalid property names. In particular data does not throw an error which has lead to some confusion due to the otherwise similar (in some cases feels almost interchangeable) behavior compared to regl.texture.

Edit: retroactive apologies for the 'should' wording.

[rreusser]

(tried to come up with a PR but that's gonna takes some time to work through where that would happen)

[mikolalysenko]

This makes some sense, could be added as a special check.