fix(mosq): install doxygen:

Author: david-cermak

.github/workflows/mosq__build.yml

@@ -83,6 +83,7 @@ jobs:
         run: |
           cd components/mosquitto
           cp api.md api_orig.md
+          pip install doxygen esp-doxybook
           ./generate_api_docs.sh
           diff -wB api.md api_orig.md
           # check version consistency