🐛 Fix build by setting node v16

The error was:
```
Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './lib/tokenize' is not defined by "exports" in /home/runner/work/gitpop3/gitpop3/node_modules/postcss-safe-parser/node_modules/postcss/package.json
    at new NodeError (node:internal/errors:405:5)
    at exportsNotFound (node:internal/modules/esm/resolve:366:10)
    at packageExportsResolve (node:internal/modules/esm/resolve:713:9)
    at resolveExports (node:internal/modules/cjs/loader:584:36)
    at Module._findPath (node:internal/modules/cjs/loader:658:31)
    at Module._resolveFilename (node:internal/modules/cjs/loader:1120:27)
    at Module._load (node:internal/modules/cjs/loader:975:27)
    at Module.require (node:internal/modules/cjs/loader:1225:19)
    at require (node:internal/modules/helpers:177:18)
    at Object.<anonymous> (/home/runner/work/gitpop3/gitpop3/node_modules/postcss-safe-parser/lib/safe-parser.js:1:17) {
  code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}
```

.github/workflows/deploy.yml

@@ -17,7 +17,9 @@ jobs:
         git config user.email github-pages-deploy-action@@users.noreply.github.com
         git remote set-url origin https://${{github.actor}}:${{github.token}}@github.com/${{github.repository}}.git
     - run: yarn install
-    - run: yarn build
+    - run: |
+        nvm install lts/gallium
+        nvm build
       env:
         REACT_APP_GRAPHQL_ENDPOINT: https://us-east1-gitpop3.cloudfunctions.net/gitpop3-graphql
         REACT_APP_SENTRY_DSN: https://46cd951350084768a0306d2c223f7805@o87984.ingest.sentry.io/5575586