Static elements

[krzema12]

There should be an opt-in way to say that e. g. all characters ['#', '|'] are static, i. e. should not be animated and no gravity should be applied to it, but they should be taken into consideration when animating the rest of the objects. Thanks to this, one could create complex scenes in some text editor, e. g. a hourglass where the glass parts are made of the static characters, and the rest of the characters is sand.

The static elements should be defined in the config using either a regex or just an array of characters (or both, alternatively).