Shop Category Overflow Fix

This mod fixes the item overflow inside build browser categories. When a build
is made at a different screen resolution than yours, the last row of items gets
cut into tiny slivers that are next to impossible to see. This reclaims the
wasted padding so a row that barely overflows fits again, and adds a scrollbar
to categories that are short on vertical space.

It's a standalone package now, so it works alongside other shop UI mods in any
load order. The only thing it can conflict with is another mod that replaces
the build category layout file itself, which is rare.

Let me know if there are any issues and I'll try to fix them as soon as I can.