doc: add addaleax to maintainers

PR-URL: #1961
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>

MAINTAINERS.md

@@ -3,6 +3,7 @@
 
 libuv is currently managed by the following individuals:
 
+* **Anna Henningsen** ([@addaleax](https://github.com/addaleax))
 * **Bartosz Sosnowski** ([@bzoz](https://github.com/bzoz))
 * **Ben Noordhuis** ([@bnoordhuis](https://github.com/bnoordhuis))
   - GPG key: D77B 1E34 243F BAF0 5F8E  9CC3 4F55 C8C8 46AB 89B9 (pubkey-bnoordhuis)