Write contribution guidelines

[lnielsen]

Write up guide on how to contribute to the guidelines.

[lnielsen]

Should include:

• Create a GitHub account
• Ask a question
• Uploading images to GitHub.
• Editing the text via GitHub.
• ReStructuredText syntax and cheat sheet.
  • Tables
  • References
  • Replacements
  • Include
  • XML examples
• Referencing issues
• Submitting a pull request. - commit message - purpose
• Discussing the pull request. - updating the pull request. - emoji - notification @mention
• How to build the docs locally
• TravisCI
• ReadTheDocs
• Spell checking
• Local checkout
• GitHub app
• Using GitHub notifications.