Add links to code of conduct from Readme and Contributing

[DeeDeeG]

Context

• Follow-up to #490
• Adds links to CODE_OF_CONDUCT.md from README.md and CONTRIBUTING.md

Summary of Changes

• CONTRIBUTING.md now has a link to the code of conduct, and a paragraph explaining what the code of conduct is about.
• README.md now has a link to the code of conduct, and a sentence mentioning what the code of conduct is about.

Checklist

• [ ] Tested Mobile Responsiveness
• [ ] Added Unit Tests
• [x] CI Passes
• [ ] Deploys to Heroku on test Correctly (Maintainers will handle)
• [ ] Added Documentation (Service and Code when required)

[DeeDeeG]

I'm not 100% sure about the wording [in Contributing.md and Readme.md], but it's [functionally] complete, and I made some effort to make sure the wording was about right, given limited time. Feedback or changes are welcome, but I would also be comfortable merging this as-is if need be.

[DeeDeeG]

Thanks for the feedback. Sounds good to me.

If there is a tad more discussion I'd feel like we could reach a real group consensus (always nice) and represent the feelings of the team as a whole, and/but in the interest of time I'm leaning toward implementing your suggestions verbatim.

If it gets to mid Sunday without updates I'll plan on doing that, since this should be merged "by the end of the week" (if I recall correctly?) -- for the Social Impact collection at GitHub. And of course we can update it as we go, and as I recall we have tended to improve README and CONTRIBUTING over time, so it's quite natural to continue doing so.

So I think we'll be fine on this, it's low pressure at this point. Just delaying 'til tomorrow to give room for further feedback and dialogue/suggestions. (If anyone at all who has contributed in the past or is thinking of doing so soon has comments/suggestions, I'd personally be open to hearing your feedback.)

[DeeDeeG]

Alright, planning to merge by the end of today.

I haven't seen any real signs of more comments coming in imminently. Still open to those, including after this is merged.

(As a minor note, I think this would be good as a "squash and merge" with a neatened up/shortened commit message. This applies cleanly on top of develop, so we don't have to merge develop into this first.)