Add e2e tests for Basics Dart examples

[chalin]

• architecture - test(e2e/dart): enable Basics chapter e2e testing #1524
• displaying-data - test(e2e/dart): enable Basics chapter e2e testing #1524
• user-input - test(e2e/dart): enable Basics chapter e2e testing #1524
• forms - test(e2e/dart): enable Basics chapter e2e testing #1524
• dependency-injection - docs(dependency-injection): revise Dart and TS code and prose #1573
• template-syntax - docs(template-syntax): review and update Dart to new doc design #1465
• cheatsheet, N/A.
• style-guide, cf. Create Dart Basics Style-Guide, prose and code #1597.
• glossary, N/A.

Contributes to #1521.

[chalin]

There is currently no plan to create a style guide. This was the only remaining subitem. Closing.