Editing Template:BuildingsNavNext/doc

This navbox end goal is to mimick the game build UI.

Dev notes:  

- Game orders category just by declaring them in order in data.categories
- Order within a category seems to be done with some "id" of who registered first? Not implemented here. 
  - (but if we need that, maybe it's enough to just add an ordering field with the same logic as the one for filter categories.)
- In game code, BuildView.lua is where most of the stuff happens
- Game filters entities by:
  - only stuff that is unlocked by faction
  - `if not frame_def.construction_recipe then return end -- not a building` -> This one matches our `entity.recipeType != Construction` in the sub template BuildingsNavCat
  - `if not bp_frame_def and not def.visual then return end -- no default visual` -> Extract code already skips this