Add a CONTRIBUTING.md and CODE_OF_CONDUCT.md and add links to those in the README.md

[Rohxn16]

This website has grown quite a lot and now that it is in full swing I have been seeing a lot more participants trying to contribute to this website. Adding a CONTRIBUTING.md to guide newcomers on how to contribute could be really useful. Also having a CODE_OF_CONDUCT.md is considered standard. Adding these will improve the community. I did not use any templates here as this is not a bug nor feature request, just some basic documentation and I am willing to submit PR to this.