Merge remote-tracking branch 'origin/main'

Author: arinming

README.md

@@ -42,6 +42,7 @@
 - [item27.md](https://github.com/Mash-Up-Android/Effective_Study/tree/main/docs/EffectiveKotlin/아린/Chapter04_추상화_설계/item27.md)
 - [item28.md](https://github.com/Mash-Up-Android/Effective_Study/tree/main/docs/EffectiveKotlin/아린/Chapter04_추상화_설계/item28.md)
 - [item29.md](https://github.com/Mash-Up-Android/Effective_Study/tree/main/docs/EffectiveKotlin/아린/Chapter04_추상화_설계/item29.md)
+- [item30.md](https://github.com/Mash-Up-Android/Effective_Study/tree/main/docs/EffectiveKotlin/아린/Chapter04_추상화_설계/item30.md)
 ### 재성
 ### Chapter01_안정성
 - [1장_독후감.md](https://github.com/Mash-Up-Android/Effective_Study/tree/main/docs/EffectiveKotlin/재성/Chapter01_안정성/1장_독후감.md)