Update getting-started.mdx

[alexnguyennz]

Description (required)

• add package manager tabs like on other setup pages so same access to npm/pnpm/Yarn commands
  • https://docs.astro.build/en/install/auto/#1-run-the-setup-wizard
  • https://docs.astro.build/en/tutorial/1-setup/2/#launch-the-astro-setup-wizard
• grammar/nitpicky - remove comma