Nominate Corentin Jabot for lambdas (llvm#114043)

Corentin has largely been handling reviews touching lambdas for the past
year or two, so he has significant understanding of the various moving
parts of this fairly substantial C++ feature. Given that work on lambdas
tends to be somewhat specialized, I think it makes sense for it to have
dedicated oversight.

clang/Maintainers.rst

@@ -78,6 +78,12 @@ Templates
 | ekeane\@nvidia.com (email), ErichKeane (Phabricator), erichkeane (GitHub)
 
 
+Lambdas
+~~~~~~~
+| Corentin Jabot
+| corentin.jabot\@gmail.com (email), cor3ntin (Phabricator), cor3ntin (GitHub)
+
+
 Debug information
 ~~~~~~~~~~~~~~~~~
 | Adrian Prantl