[libclc] Propose new libclc maintainer (llvm#161141)

Wenju He has been active on the libclc project for a while now and has
been contributing to the overall health and steering the future of the
project.

Author: frasercrmck

libclc/Maintainers.md

@@ -10,6 +10,9 @@ The following people are the active maintainers for the project. Please reach
 out to them for code reviews, questions about their area of expertise, or other
 assistance.
 
+Wenju He \
+[email protected] (email), [wenju-he](https://github.com/wenju-he) (GitHub)
+
 Tom Stellard \
 [email protected] (email), [tstellar](https://github.com/tstellar) (GitHub)