zig -> html

generates hyperlinked html from zig source files

this sort of depends on https://github.com/ziglang/zig/issues/2206, 
which has been accepted but not implemented

would also be useful to have identifiers link to where they're from,
but i guess that's on the backburner.
in its current stage, this is sort of just a proof of concept.

usage
    zig build-exe zightml.zig
    ./zightml /path/to/files

todo
    it would be useful to link identifiers as well (when you click one, it goes to its definition)

    linking packages (e.g. @import("std"), @import("some_package")) - 
    could also link @import("root") and @import("builtin") to documentation pages
 
prior art
    https://agda.github.io/agda-stdlib/
    https://github.com/kristoff-it/zig-doctest/
    https://ratfactor.com/zig/stdlib/