split feature exports/builds into different "packages"

[eugpoloz]

I would like to split this into 3 distinctive modules — at the very least for html-header, html-footer, and main-reply. Idk what I actually need for this, maybe this calls for something like a monorepo structure or something?

Anyway, that's the main idea—and it could be useful for leveraging native FORUM functions, too! Less config and stuff.