Introduce a way to show config warnings in swaynag

Adds the function `config_add_swaynag_warning(char *fmt, ...)` so that
handlers can add warnings to the swaynag config log in a uniform way.
The formatting is identical to errors and include the line number, line,
and config path.

This also alters the background file access warning to use the function
and introduces a warning for duplicate bindings.

0 files changed, 0 insertions, 0 deletions