Anti-aliased text is not something desired for every situation, a tick box for enabling/disabling it would be a simple but effective addition to the engine.
The reason this is not already supported is because browsers currently don't provide a way to turn off text anti-aliasing in canvases. (There are some CSS options for this, but they don't affect canvas text rendering.) To get this supported you'd need to approach the browser vendors instead.
In the mean time one workaround is to use the alpha clamp shader on the text object. This defaults to a 50% alpha cutoff, so the soft edges become either fully opaque at >50% alpha, or fully transparent at <50% alpha.