docs fix spelling issues

CONTRIBUTING.md

@@ -30,7 +30,7 @@ All other branches should be assumed to be miscellaneous feature development bra
 All downstream users of the library should be using tagged versions of the library pulled from cargo.
 
 ## How to work on a fork
-Please skip this section if you're familiar with contributing to opensource github projects.
+Please skip this section if you're familiar with contributing to open source github projects.
 
 First fork the repo from the github UI, and clone it locally.
 Then in the repo, you want to add the repo you forked from as a new remote. You do this as:
@@ -62,4 +62,4 @@ and either refer to the relevant section of a paper or include a short proof/arg
 All performance improvements should be accompanied with benchmarks improving, or otherwise have it be clear that things have improved.
 For some areas of the codebase, performance roughly follows the number of field multiplications, but there are also many areas where
 hard to predict low level system effects such as cache locality and superscalar operations become important for performance.
-Thus performance can often become very non-intuitive / diverge from minimizing the number of arithmetic operations.
+Thus performance can often become very non-intuitive / diverge from minimizing the number of arithmetic operations.