Adds esp_mqtt_cxx component

- Component moved from esp-idf
- Files moved to adjust to esp-protocol structure

components/esp_mqtt_cxx/docs/conf_common.py

@@ -0,0 +1,23 @@
+# flake8: noqa
+from esp_docs.conf_docs import *
+
+extensions += [
+    'sphinx_copybutton',
+    # Needed as a trigger for running doxygen
+    'esp_docs.esp_extensions.dummy_build_system',
+    'esp_docs.esp_extensions.run_doxygen',
+]
+
+# link roles config
+github_repo = 'espressif/esp-protocols'
+
+# context used by sphinx_idf_theme
+html_context['github_user'] = 'espressif'
+html_context['github_repo'] = 'esp-docs'
+
+# Extra options required by sphinx_idf_theme
+project_slug = 'esp-idf'  # >=5.0
+versions_url = 'https://github.com/espressif/esp-protocols/docs/docs_versions.js'
+
+idf_targets = ['esp32']
+languages = ['en']