ide: ignore ide specific settings in favor of gradle

Avoid influencing local builds. This shall be fully done via gradle.

Author: Pfeil

.gitignore

@@ -18,6 +18,9 @@ bin
 # Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
 # Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
 
+# Actually we want to make sure everything is handled via gradle.
+.idea
+
 # User-specific stuff
 .idea/**/workspace.xml
 .idea/**/tasks.xml