refactor: update contributing guidelines

CONTRIBUTING.md

@@ -2,11 +2,11 @@
 
 We love your input! 🚀 We want to make contributing to this project as easy and transparent as possible, whether it's:
 
--   Reporting a bug
--   Discussing the current state of the code
--   Submitting a fix
--   Proposing new features
--   Becoming a maintainer
+-   Reporting a bug.
+-   Discussing the current state of the code.
+-   Submitting a fix.
+-   Proposing new features.
+-   Becoming a maintainer.
 
 ## We Develop with Github
 
@@ -37,13 +37,13 @@ We use GitHub issues to track public bugs. Report a bug by [opening a new issue]
 
 **Great Bug Reports** tend to have:
 
--   A quick summary and/or background
--   Steps to reproduce
+-   A quick summary and/or background.
+-   Steps to reproduce.
     -   Be specific!
-    -   Give sample code if you can. [My stackoverflow question](http://stackoverflow.com/q/12488905/180626) includes sample code that _anyone_ with a base R setup can run to reproduce what I was seeing
--   What you expected would happen
--   What actually happens
--   Notes (possibly including why you think this might be happening, or stuff you tried that didn't work)
+    -   Give sample code if you can. [My stackoverflow question](http://stackoverflow.com/q/12488905/180626) includes sample code that _anyone_ with a base R setup can run to reproduce what I was seeing.
+-   What you expected would happen.
+-   What actually happens.
+-   Notes (possibly including why you think this might be happening, or stuff you tried that didn't work).
 
 People _love_ thorough bug reports. I'm not even kidding.