E2E tests for the local filesystem sync

[adamziel]

Let's E2E test syncing Playground files with a local directory

Related:

• https://github.com/WordPress/wordpress-playground/pull/548
• https://github.com/WordPress/wordpress-playground/issues/196
• https://github.com/WordPress/wordpress-playground/pull/547
• https://github.com/WordPress/wordpress-playground/pull/802
• https://github.com/WordPress/wordpress-playground/issues/765

[adamziel]

Relevant and related:

• https://github.com/microsoft/playwright/issues/6854
• https://playwright.dev/docs/api/class-filechooser