Document use of `beam_files`

[Paulo F. Oliveira]

We should add a generic section stating some analysis types work over .beam files and then, per rule, have a "Works on .beam?" reference.

e.g.

beam_files

Certain rules (signaled with "Works on .beam file? Yes!") allow you to perform analysis directly on beam files (instead of source code).

Though this analysis may be useful for pin-pointing certain elements, beware that, e.g., reported line_numbers will most surely not corresponding to those in the source file.

[Paulo F. Oliveira]

This has been added to the Rules wiki.