Feat: Added `.accessibleName()` as an alias for `.getAccessibleName()`.

fixes #4177

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[ . ] Before marking your PR for review, please test and verify your changes by making appropriate modifications to any of the Nightwatch example tests (present in examples/tests directory of the project) and running them. ecosia.js and duckDuckGo.js are good examples to work with.
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[ . ] If you're fixing a bug also create an issue if one doesn't exist yet;
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nightwatchjs / nightwatch