feat(tools): unified container dev setup (#65589)

.devcontainer/README.md

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+# To start developing:
+
+Wait for the container to build and start. You will see "Done. Press any key to close the terminal." in the terminal when it's ready. 
+
+Once it's running, you can start the development server:
+
+**Option 1:** Press `Ctrl+Shift+P`, type "Run Task", select "Start Development"
+**Option 2:** Open a terminal and run:
+
+```bash
+pnpm run develop
+```
+
+## Optional setup
+
+For E2E tests:
+
+```bash
+npx playwright install chromium
+```
+
+For curriculum tests:
+
+```bash
+pnpm -F=curriculum install-puppeteer
+```
+
+## More information
+
+For detailed setup instructions and contribution guidelines, visit:
+https://contribute.freecodecamp.org/how-to-setup-freecodecamp-locally