Rename "beginner" to "good first issue" (MunGell#151)

README.md

@@ -49,7 +49,7 @@ If you are an open source project maintainer, add the label `first-timers-only`
 
 - [TEAMMATES](https://github.com/TEAMMATES/teammates/labels/d.FirstTimers) _(label: d.FirstTimers)_ <br> TEAMMATES is a free online tool for managing peer evaluations and other feedback paths of your students.
 - [elasticsearch](https://github.com/elastic/elasticsearch/labels/low%20hanging%20fruit) _(label: low hanging fruit)_ <br> Open Source, Distributed, RESTful Search Engine.
-- [JabRef](https://github.com/JabRef/jabref/labels/beginner) _(label: beginner)_ <br> Desktop application moving from SWING to JavaFX. Focus on code quality: Usage of code quality tools such as [CodeCov](https://codecov.io/) and [Codacy](https://www.codacy.com/). Each Pull Request is reviewed by two developers to provide high-quality feedback and to ensure high quality of new contributions.
+- [JabRef](https://github.com/JabRef/jabref/labels/good%20first%20issue) _(label: good first issue)_ <br> Desktop application moving from SWING to JavaFX. Focus on code quality: Usage of code quality tools such as [CodeCov](https://codecov.io/) and [Codacy](https://www.codacy.com/). Each Pull Request is reviewed by two developers to provide high-quality feedback and to ensure high quality of new contributions.
 - [Wikimedia Commons Android App](https://github.com/commons-app/apps-android-commons/labels/beginner%20friendly) _(label: beginner friendly)_ <br> Allows users to upload pictures from their Android phone/tablet to Wikimedia Commons.
 
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