add ref to learning guide for people to get started

as it is possible people get interested in tower,
but are not yet advanced enough in their learning journey
to understand (already) the more difficult parts
of the codebase

Author: glendc

README.md

@@ -112,6 +112,11 @@ note that:
 The documentation also contains some smaller examples and of course the codebase can be read as well,
 together with its unit tests.
 
+> Are you still new to Rust, or feel you have much to learn on your Rust learning journey?
+> You might find it useful to use <https://rust-lang.guide/> as your learning guide,
+> which might also help you get you on your way to understand the more complicated parts
+> of this monorepo codebase.
+
 ## Sponsorship
 
 Regular and onetime sponsors alike help us to pay the development and service costs