Update README.md

Author: gares

README.md

@@ -109,6 +109,8 @@ and `ocaml-lsp-server` (version 1.15).
   and tactics are represented, how to handle tactic arguments and finally how
   to define tactic notations. It assumes the reader is familiar with Elpi and
   the HOAS of Coq terms.
+- [Elpi: rule-based meta-language for Rocq](https://www.youtube.com/watch?v=XjkpA5rVxkM)
+  video recording of the keynote at CoqPL25.
 - [Coq-Elpi in 20 minutes](https://youtu.be/m60rHnvCJ2o)
   video recording of a talk given at the Coq Users and Developers Workshop 2020.