Update contributing possibilities

[lappemic]

At the moment the contributing guidlines mention only how to add a project or join the community, but not e.g. how to contribute to the website itself. I think it would be nice to encourage people to contribute to the website itself as well if they see potential of improvements, correct typos, or other issues.

Suggested changes

• Update Contributing.md to include encouragment and instructions on how to make changes for the website
• Update the codebase to facilitate changes on the website for new contributers (e.g. add a requirements file, update .gitignore with virtualenvs, etc.)

If this is something you also think is worth doing, let me know. I would make the needed changes with pleasure.