chore: configure chromatic snapshot tests (#896)

Resolves: #444

Summary:

This commit installs and configures a GH action for chromatic. Chromatic
is used for snapshot testing build-over-build.

Details:

* chore: install chromatic

* chore: add chromatic package.json script

Suggested by the docs for convenience so that we can run chromatic like:

```console
yarn run chromatic ...
```

* chore: gitignore storybook builds

* ci: configure chromatic

This action configures chromatic to run in CI on pushes to all branches.
By running this in CI, we get the following:

- snapshot (build-over-build)
- checks in our CI

The snapshots and build-over-build behavior are per branch; this way we
can work on a feature branch without worrying about changes being made
to mainline independently.

* chore: remove manual storybook build from CI

This is now the responsibility of Chromatic

site/package.json

@@ -7,6 +7,7 @@
     "postinstall": "yarn typegen",
     "build": "NODE_ENV=production webpack build --config=webpack.prod.ts",
     "build:analyze": "NODE_ENV=production webpack --profile --progress --json --config=webpack.prod.ts > out/stats.json && webpack-bundle-analyzer out/stats.json out",
+    "chromatic": "chromatic",
     "dev": "webpack-dev-server --config=webpack.dev.ts",
     "format:check": "prettier --check '**/*.{css,html,js,json,jsx,md,ts,tsx,yaml,yml}'",
     "format:write": "prettier --write '**/*.{css,html,js,json,jsx,md,ts,tsx,yaml,yml}'",
@@ -59,6 +60,7 @@
     "@typescript-eslint/eslint-plugin": "5.17.0",
     "@typescript-eslint/parser": "5.17.0",
     "@xstate/cli": "0.1.5",
+    "chromatic": "6.5.3",
     "copy-webpack-plugin": "10.2.4",
     "css-loader": "6.7.1",
     "css-minimizer-webpack-plugin": "3.4.1",

site/yarn.lock

@@ -5484,6 +5484,11 @@ chownr@^2.0.0:
   resolved "https://registry.yarnpkg.com/chownr/-/chownr-2.0.0.tgz#15bfbe53d2eab4cf70f18a8cd68ebe5b3cb1dece"
   integrity sha512-bIomtDF5KGpdogkLd9VspvFzk9KfpyyGlS8YFVZl7TGPBHL5snIOnxeshwVgPteQ9b4Eydl+pVbIyE1DcvCWgQ==
 
+chromatic@6.5.3:
+  version "6.5.3"
+  resolved "https://registry.yarnpkg.com/chromatic/-/chromatic-6.5.3.tgz#dd96e6df6d2ed9d0c79277dc18b06a089080ce62"
+  integrity sha512-6Wy2lsNaojY5wTvobE3WV5VrQ5oP7B8kal6zWGrxu9g7Qbenb2cTcQ5SYgQY7tzT0Ed0zeHVyQm4TMmKz+XfXA==
+
 chrome-trace-event@^1.0.2:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/chrome-trace-event/-/chrome-trace-event-1.0.3.tgz#1015eced4741e15d06664a957dbbf50d041e26ac"