feat(tools): remove eslint-plugin-prettier for prettier (#42438)

* feat: remove eslint-plugin-prettier for prettier

This removes the annoying lint warnings when all that needs to change is
formatting

* fix: use .js lint-staged config to ignore properly

* fix: lint everything if a lot of files are changed

It's faster than making lots of individual linter calls

* chore: apply prettier

* fix: ignore code in curriculum-file-structure

.lintstagedrc.js

@@ -0,0 +1,28 @@
+const { ESLint } = require('eslint');
+
+const cli = new ESLint();
+
+// if a lot of files are changed, it's faster to run prettier/eslint on the
+// whole project than to run them on each file separately
+module.exports = {
+  '*.(js|ts|tsx)': files =>
+    files.length > 10
+      ? ['eslint --max-warnings=0 --cache --fix .', 'prettier --write .']
+      : [
+          'eslint --max-warnings=0 --cache --fix ' +
+            files.filter(file => !cli.isPathIgnored(file)).join(' '),
+          ...files.map(filename => `prettier --write '${filename}'`)
+        ],
+  '*.!(js|ts|tsx)': files =>
+    files.length > 10
+      ? 'prettier --write .'
+      : files.map(
+          filename => `prettier --write --ignore-unknown '${filename}'`
+        ),
+  './curriculum/challenges/**/*.md': files =>
+    files.length > 10
+      ? 'npm run lint:challenges'
+      : files.map(
+          filename => `node ./tools/scripts/lint/index.js '${filename}'`
+        )
+};