add build artifacts to .gitignore

Exclude obj/ and .gradle/ directories to prevent build artifacts from showing as untracked files.

Author: Tom-Dynamsoft

.gitignore

@@ -41,6 +41,10 @@ yarn.lock
 /.gitattributes
 /.*ignore
 
+# Build artifacts
+obj/
+.gradle/
+
 !bower.json
 !composer.json
 !package.js