add box2d submodule

Birch-san · Birch-san · commit 4004eff230c7 · 2020-10-07T11:14:15.000+01:00
diff --git a/.gitmodules b/.gitmodules
@@ -0,0 +1,4 @@
+[submodule "box2d"]
+	path = box2d
+	url = git@github.com:erincatto/box2d.git
+	branch = master
diff --git a/box2d b/box2d
@@ -0,0 +1 @@
+Subproject commit f0f9d50a328a709cc3a287a61b864e7d0e3ef35f
