Squashed 'third_party/pico-sdk/' content from commit 2062372d2

Change-Id: Ic20f199d3ed0ea8d3a6a1bbf513f875ec7500cc6
git-subtree-dir: third_party/pico-sdk
git-subtree-split: 2062372d203b372849d573f252cf7c6dc2800c0a
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..4846c9c
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "tinyusb"]
+	path = lib/tinyusb
+	url = https://github.com/hathach/tinyusb.git