fix: implement handle_info/2

[francois-codes]

When running the project again, I noticed some errors I didn't see before in the output:

This messages correspond to the messages sent by the nodejs for warnings and debugging info.

This PR fixes the problem by implementing the handle_info/2 method, as advised in the error message. In order to avoid the spam, I added a check for Mix.env() to make sure we were only showing this information in dev.

This is the equivalent of the command above with this PR:

FYI @Valian @grossvogel

[francois-codes]

@grossvogel do you think you could have a look at this ?