Add support for file suffixes

[dbrgn]

To simplify cache busting, it would be great if there were an option to add e.g. a profilesSuffix, analogous to the profilesPrefix option (and the same for memoryInitializerPrefix and libfecPrefix).

In my project I set HTTP caching to 1 year for all static resources and use a ?v=123 parameter that is incremented on each release.

[brian-armstrong]

@dbrgn

This is a good idea, and I believe it'd be easy enough to do with the profiles. Unfortunately I'm not sure it'll work for the emscripten bits since that tends to be more inflexible.

I've got a big overhaul planned on how all the fetching stuff works since it's presently pretty brittle. I'll see what I can do with suffixes as part of that