Add .gitignore to exclude binary from commits

Co-authored-by: leereilly <121322+leereilly@users.noreply.github.com>

Author: Copilot

.gitignore

@@ -0,0 +1,18 @@
+# Binaries
+gh-dungeons
+
+# Build artifacts
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool
+*.out
+
+# Go workspace file
+go.work