Add .gitignore for build artifacts

FreeBSD User

db6411c4ea6a9a92527486c0461b402ae5362deb

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..edcc946
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+# Chez Scheme compiled library caches
+*.so
+*.wpo
+
+# CDB data files
+*.cdb