According to the documentation for the atom program , the initialization file init.coffee searched for by the atom program in the ~/.atom .
if there is no such file, you can create it.
This file is interpreted by the atom program after the download is complete.
The ex-mode package documentation says that examples are in the file lib/ex.coffee . this is a relative path from the directory with this package. i.e., ~/.atom/packages/ex-mode/lib/ex.coffee .
there, in the documentation, an example of the configuration is also given, which must be inserted directly into the aforementioned initialization file init.coffee .