Added documentation line on default editor

readme.md

@@ -55,6 +55,7 @@ npm install -g gitlab-time-tracker
 ```
 
 Run the config command to create a config file and open it in your default editor.
+In linux terminal, you must set your preferred editor in the environment. For example, use `export EDITOR=vim` to edit the files with vim (put this in `.bashrc` or similar to have it always configured).
 If nothing happens, open the file manually: `~/.gtt/config.yml` - on Windows: `C:\Users\YourUserName\.gtt\config.yml`
 
 ```shell