Best practices: refine section about "compiled in absolute paths"

We need a better section on resource lookups. The section in question is *very* specific. However it is generally a good idea to look up resources relative to the main binary, and one doesn't require `binreloc` for it.

Generally it should be named something like "Look up resources in a way that supports relocation" or so.

CC https://github.com/aardappel/treesheets/issues/130