Update Dockerfile

try to fix the maintainability issue

apps/generator/Dockerfile

@@ -12,10 +12,9 @@ ENV PUPPETEER_SKIP_CHROMIUM_DOWNLOAD true
 # Since 0.14.0 release of html-template chromium is needed for pdf generation.
 # More custom packages for specific template should not be added to this dockerfile. Instead, we should come up with some extensibility solution.
 # The --no-cache prevents from caching of the package index which saves space by not storing the APK cache files.
+# Install dependencies and AsyncAPI Generator in a single RUN command
 RUN apk --no-cache add git chromium && \
-    rm -rf /var/cache/apk/*
-
-# Installing latest released npm package
-RUN npm install -g @asyncapi/generator@$ASYNCAPI_GENERATOR_VERSION
+    rm -rf /var/cache/apk/* && \
+    npm install -g @asyncapi/generator@$ASYNCAPI_GENERATOR_VERSION
 
 ENTRYPOINT [ "ag" ]