chore: update dependencies to latest minor version

[m2mathew]

NOTE

I changed the "main" branch from master to main. People might need to update their forks.

The issue

We are getting a lot of "vulnerability" warnings from GitHub about outdated packages

The solution

• Upgrade packages to latest minor version
  • Need to do more, but the transition to Gatsby v3 needs to be its own PR work
• Add two new scripts for some handy helpers and update a third one:
  • dev: runs the app (used to be develop)
  • clean:gatsby: runs gatsby clean
  • clean:purge: removes all node modules then runs 'yarn cache clean`
• Require node 12.x

Visuals

Before	After

Test cases

0. Make sure you are on node version 12.x
1. Get this code
2. Run yarn
3. Run yarn dev and make sure the app builds correctly

[sriverag]

@m2mathew - Re: 0. Make sure you are on node version 12.x: We should add a .nvmrc in order to specify the supported Node version for the project.
It will be easier to enforce the version if using this shell script to do nvm use [version specified in .nvmrc] automatically: https://github.com/nvm-sh/nvm/blob/master/README.md#deeper-shell-integration