Add third_parties/OpenTDC as a submodule

.gitmodules

diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..bcdde35
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "third_parties/OpenTDC"]
+	path = third_parties/OpenTDC
+	url = https://github.com/tgingold/OpenTDC.git

third_parties/OpenTDC

diff --git a/third_parties/OpenTDC b/third_parties/OpenTDC
new file mode 160000
index 0000000..2d6dc65
--- /dev/null
+++ b/third_parties/OpenTDC
@@ -0,0 +1 @@
+Subproject commit 2d6dc6598c0af333c2a12bd2ff1ddd902033cc69