gitignore: clarify 5 comments

Author: stephengold

.gitignore

@@ -1,17 +1,17 @@
-# Ignore Gradle project-specific cache directory
+# Ignore Gradle's project-specific cache directory:
 .gradle
 
-# Ignore Gradle build output directory
+# Ignore Gradle's build output directories:
 build
 bin
 
-# Native libraries that get extracted when apps are run
+# Ignore native libraries that get extracted when apps are run:
 *.dll
 *.so
 
-# Captured screenshots and video
+# Ignore captured screenshots and videos:
 /*.avi
 /*.png
 
-# Development environment
+# Ignore IDE-specific directories:
 /.idea/