Exclude node_modules from docker context

Change-Id: I1e83bb59280801d86692e4fe69d85cd484f56b20
diff --git a/.dockerignore b/.dockerignore
index fdc39b0..8d94c00 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -6,3 +6,5 @@
 .git
 .gitignore
 
+# npm
+**/node_modules