[docs] added ability to add static pages in docs folder and README.md in modules and doctypes

docs/docs.md

@@ -0,0 +1,11 @@
+---
+{
+	"_label": "Documentation"
+}
+---
+Welcome to the ERPNext Developer documentation.
+
+The documentation is split into two parts.
+
+- Part 1 covers the code and all functions, methods available
+- Part 2 covers all the models in the product including core models