Adding columbus project as submodule

.gitmodules

diff --git a/.gitmodules b/.gitmodules
index c73b442..d660bde 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,6 @@
 [submodule "caravel-lite"]
 	path = caravel
 	url = https://github.com/efabless/caravel-lite
+[submodule "columbus"]
+	path = columbus
+	url = https://gitlab.com/skywater130/columbus.git

columbus

diff --git a/columbus b/columbus
new file mode 160000
index 0000000..7771593
--- /dev/null
+++ b/columbus
@@ -0,0 +1 @@
+Subproject commit 77715938ac822cdc2917213fefa6fbed6d4a0aea