Feature request: Exclude packages / directories

I use [JHipster](https://www.jhipster.tech/) which generates a Spring Boot / Angular project for me. Now I don't want to format the generated code I never touch. That's why I need to exclude Java packages/directories from formatting.

I believe I can do this in the Google Java Format Gradle plugin. I'd like to exclude Java packages/directories in the IntelliJ plug-in, too.

該 issue 未指出任何檔案、測試或 IntelliJ 入口點。首先定位 IntelliJ 外掛程式的格式化路徑，並將其設定與 Gradle 外掛程式的套件或目錄排除項進行比較；完成的標準是，被排除的 Java 套件和目錄會被 IntelliJ 格式化略過，並且有測試涵蓋。

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