cloud-sql-proxy: add shell completion

Author: Moisan

Formula/c/cloud-sql-proxy.rb

@@ -19,6 +19,7 @@ class CloudSqlProxy < Formula
 
   def install
     system "go", "build", *std_go_args(ldflags: "-s -w")
+    generate_completions_from_executable(bin/"cloud-sql-proxy", "completion", shells: [:bash, :zsh, :fish, :pwsh])
   end
 
   test do