Currently, if a window class is specified in the swallow_regex (e.g.
Kitty) it will swallow every other window spawned by it automatically.
Many other WMs implementing this functionality allow for defining
exceptions from this rule. For instance, we want Kitty to swallow sxiv
or zathura but we do not want Kitty to swallow something like wev.
This commit adds an additional regex - swallow_exception_regex where
these exceptions can be defined. This regex is then compared against the
title of the window about to be swallowed and if it happens to be a
match, aborts the swallowing.
This works because whenever an application that could be swallowed is
launched by a terminal, the class of the terminal remains the same while
the title changes to whatever the application's name is, thus letting it
be matched against a regex.
efee6a1cda