Update runtime files
diff --git a/runtime/syntax/livebook.vim b/runtime/syntax/livebook.vim
new file mode 100644
index 0000000..133cab0
--- /dev/null
+++ b/runtime/syntax/livebook.vim
@@ -0,0 +1,8 @@
+" Placeholder Livebook syntax file.
+" This simply uses the markdown syntax.
+
+if exists("b:current_syntax")
+    finish
+endif
+
+runtime! syntax/markdown.vim