Add .gitignore for target/

The crate builds into the workspace's shared target dir today, but a
standalone build here would create one that nothing ignored.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

 .gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b83d222
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target/