embedding content a markdown file

Based on issue #14 - many thanks to @lorenaSalome

To include images or other files in the reflections or score markdown:

1. add the image/other files to the folder '/extensions' (create it if it doesn't yet exist).

2. Tell git to track the new image

git add /extensions/nameOfImageFile.png

3. in the markdown file (i.e. score.md), embed the image using relative path syntax:

![image name or some text or whatever](extensions/nameOfImageFile.png)

For reference, this github user demonstrates in detail:

https://github.com/mark-anders/relative-image-url