Fix indentation in getting_started/README.md
Fix indentation in getting_started/README.md

The bullet points for each OS were formatted all on one line, which
looks pretty gross.

Signed-off-by: Cullen Taylor <0a4f58109a9f9b7b2781cb48fa62bfe7918cb3d0@outlook.com>

BonnyCI/bonnyci.org,BonnyCI/bonnyci.org,BonnyCI/bonnyci.org,BonnyCI/bonnyci.org