signoff design files

Signed-off-by: Ruige <295054118@whut.edu.cn>
diff --git a/openlane/user_proj_example/timing.sdc b/openlane/user_proj_example/timing.sdc
new file mode 100644
index 0000000..8318e12
--- /dev/null
+++ b/openlane/user_proj_example/timing.sdc
@@ -0,0 +1,5 @@
+set_false_path -from io_in[28]
+set_false_path -from io_in[34]
+set_false_path -from io_in[35]
+set_false_path -from io_in[36]
+set_false_path -from io_in[37]