test(counters_stable): add playwright tests

[agilarity]

READY FOR REVIEW

Add Playwright tests for the counters_stable example.

Changes

• Add cargo make tasks for Trunk and Playwright
• Add tests the following scenarios:
  • Add 1000 Counters › should increment the total count by 1K
  • Add Counter › should increment the total count
  • Clear Counters › should reset the counts
  • Decrement Count › should decrement the total count
  • Increment Count › should increment the total count
  • View Counters › should_see_the_title
  • View Counters › should see the initial counts

VERIFICATION

• Run cargo make ci from examples/counters_stable directory (ci is an alias for verify-flow)

Notes

• I opened an issue about flaky tests: test(counters_stable): intermittent closed target errors #1240