Fixed a typo, first commit.

Summary: fixed a typo on contributing md file.

Test Plan: just read the file to check the changes.

Reviewers: lynorian

Reviewed By: lynorian

Subscribers: lynorian

Differential Revision: https://phab.lubuntu.me/D89

CONTRIBUTING.md

@@ -56,9 +56,9 @@ Contents
    20/foo_bar
 ```
 
-Then run `make clean && make html && make latexpdf` in the root of the manual directory and it should build successfully with zero wanrings!
+Then run `make clean && make html && make latexpdf` in the root of the manual directory and it should build successfully with zero warnings!
 
-## Getting mulitple Versions to Work
+## Getting multiple Versions to Work
 To change into the file for the code you cloned from git of sphinxconfig-versioning and run ``` cd sphinxcontrib-versioning && sudo python3 setup.py install```
 
 ## Making changes and seeking your changes to be pulled