Add Ballerina gitignore file

Ballerina.gitignore

@@ -0,0 +1,11 @@
+# Ballerina generates this directory during the compilation of a package. 
+# It contains compiler-generated artifacts and the final executable if this is an application package.
+target/
+
+# Ballerina maintains the compiler-generated source code here.
+# Remove this if you want to commit generated sources.
+generated/
+
+# Contains configuration values used during development time.
+# See https://ballerina.io/learn/provide-values-to-configurable-variables/ for more details.
+Config.toml