Add node version lock

AjaiKN · AjaiKN · commit 8918863e8ab9 · 2021-04-28T23:37:29.000-04:00
diff --git a/phoenix_static_buildpack.config b/phoenix_static_buildpack.config
@@ -0,0 +1,2 @@
+# Node.js version
+node_version=15.12.0
