Add .gitignore to sw/tock_matcha

Change-Id: I45c66953635ec0510a276baa50c0ce003e348c61

.gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..fa8d85a
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+Cargo.lock
+target