internal: add gitignore

Change-Id: Ibc2891eada910a62ae60791c490d977fc99191c9
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/50111
Reviewed-by: Tyler Bui-Palsulich <tbp@google.com>
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ee9694b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,11 @@
+# Editors
+.idea
+.vscode
+*.swp
+
+# Test files
+*.test
+coverage.txt
+
+# Other
+.DS_Store