Include the .md extension on CONTRIBUTING and LICENSE

[chase-mortensen]

What is the improvement? Github formats markdown files nicely, but it doesn't recognize these files as being markdown since they are missing the extension. Additional context I think this small fix would improve the readability of these files. I plan on making a PR.

Side note: This is my first issue/PR, so any suggestions are welcome. Thanks

[kevinmahrous]

Oh thanks for making PR.

[kevinmahrous]

Thanks again