fix: color of selected country in footer

[piperchester]

When selected, the country is difficult to read in the footer:

This is a tiny PR to make the selected color white.

Also,

• Added install instructions to CONTRIBUTING.md
• Removed extraneous period from selected country (was a subjective call; happy to back this out if undesired!)

This project is fantastic and I'm a big fan. @ maintainers, would it be possible for me to get push permissions so that I don't need to fork the repo to contribute?

[philsturgeon]

Thank you! The selected country doesn't work too well right now, and our plans for a rewrite have gone up in smoke due to inactivity. Life is hard and people have jobs, so it happens. Do you think you could take a stab at #28 for this gatsby based site?

[piperchester]

Thank you! The selected country doesn't work too well right now, and our plans for a rewrite have gone up in smoke due to inactivity. Life is hard and people have jobs, so it happens. Do you think you could take a stab at #28 for this gatsby based site?

Yes! I can take a look.

Wildly unrelated, do you think there's value in getting protect.earth into hacktoberfest?

[philsturgeon]

We're probably about to merge protect.earth with climatechoice.co which will require a fair bit of open-source help. We had some plants to do things rather differently for a while but at this point I think the plan is to make an airtable, switch this v1 over to https://www.gatsbyjs.com/plugins/gatsby-source-airtable/, then we can use that same table to power the directory on climatechoice.co (or whichever other directory we merge with) and we can then deprecate the directory on our site as protect.earth starts to focus on reforestation.

If you'd be willing to help with any of all of the above that'd be amazing, but I'd hate for anyone to labor under false pretenses.