gitignore: Add a few lines following an upstream change

chrisbobbe · chrisbobbe · commit 4c2e671fa04c · 2024-09-03T15:30:56.000-07:00
This change has been getting applied by `flutter run`, and Greg identified this upstream commit as the cause: flutter/flutter@29f332c82 Discussion: #873 (comment)
diff --git a/.gitignore b/.gitignore
@@ -5,9 +5,11 @@
 *.swp
 .DS_Store
 .atom/
+.build/
 .buildlog/
 .history
 .svn/
+.swiftpm/
 migrate_working_dir/
 
 # IntelliJ related
