add a way to add own bash aliases

simple as that - it gives us the flexibility to add our own aliases without breaking (or at least changing) anything in the original repo
You have syntax error here.
Furthermore I don't want to specify the exact path here. You have a special variable ```$slim_path``` available which points to a directory in which slimsh is installed. 

A better version of it would be something like 
```bash
if [[ -f $slim_path/aliases.zsh.local ]]; then
 source $slim_path/aliases.zsh.local
fi
```