How to order collections in the left menu

[digitalfredy]

Hello,

Following #100 where the collections usage was proposed I was capable to group parts of my document and it is great but now I have a problem, I can no put those collections in the right order.

Think I have those collections:

• Start
• End

Unfortunately the left menu do his index in alphabetical order then it shows first all the content related with the End and then all the content related with the Start which is not great for a book

I guess the easiest way (as user) is to use the same order they are written in the _config.yml file