fix(docs): add echo statements for documentation build process clarity

Author: oujago

.readthedocs.yml

@@ -14,9 +14,11 @@ build:
       # Copy the appropriate conf.py based on project name
       - |
         if [ "$PROJECT_VERSION" = "brainpy-version2" ]; then
+          echo "Building brainpy-version2 documentation"
           mkdir -p docs_build
           cp -r docs_version2/* docs_build/
         else
+          echo "Building standard brainpy documentation"
           mkdir -p docs_build
           cp -r docs/* docs_build/
         fi