Adding Linting and Formatting (#77)

Addresses #11 item "Linting/formatting (eg eslnt, prettier)":
* Adding eslint, prettier, and config targeting Google, typescript, and both nodejs and client builds
* Addressing linter-found issues
* Adding lint and lint:fix commands
* Adding documentation
* Renaming workflow and adding lint check
* Adding documentation about VSCode linting/formatting, ran formatting on a few files, set up exclude list for gatsby develop, setup build to fail on error

client/README.md

@@ -1,5 +1,25 @@
 # Justice40 Client
 
+## Linting and Formatting
+
+This project uses [ESLint](https://eslint.org/) for code linting and [Prettier](https://prettier.io/) for formatting. They are integrated via [gatsby-plugin-prettier-eslint](https://www.gatsbyjs.com/plugins/gatsby-plugin-prettier-eslint/).
+
+Linting is a required check before merges can happen, please lint your code, for the sake of consistency!
+
+To use:
+
+1. During development:
+
+   1. `npx gatsby develop` will automatically run prettier and eslint during development as files change, watch the console for updates.
+   2. Alternatively, if you're using VSCode:
+      1. Install the [Prettier](https://marketplace.visualstudio.com/items?itemName=esbenp.prettier-vscode) and [ESLint](https://marketplace.visualstudio.com/items?itemName=dbaeumer.vscode-eslint) plugins
+      2. Enable `editor.formatOnSave`, and optionally `"editor.codeActionsOnSave": {"source.fixAll": true},` to apply settings on save
+
+2. Before a PR: `npm run lint:fix` can be run locally to apply auto-fixes to issues that can be fixed
+3. Before merge (automatic): `npm run lint` is run against all PRs by a github action.
+
+The ruleset is simply the base ruleset + [Google](https://github.com/google/eslint-config-google).
+
 ## Localization
 
 ### About