Add resilience test, improve README, implementation refinement

Key Features ✨

• Added resilience test: Covers a mixed scenario with both successful and failed tasks.
• Enhanced README: Introduced a Check-and-Abort use case example.
• Implementation refinement: Removed the unused _currentlyExecutingTask internal property, which became irrelevant as of version 1.1.2. Originally, it tracked the task in progress but was replaced with _waitForAvailability, as the latter does not throw.