TODO: add symlink to TODO.md

Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/TODO b/TODO
new file mode 120000 (symlink)
index 0000000..cde952b
--- /dev/null
+++ b/TODO
@@ -0,0 +1 @@
+TODO.md
\ No newline at end of file