[Example] add example for nextjs app and discord/slack bots (#1111)

Co-authored-by: Deven Patel <deven298@yahoo.com>

examples/nextjs/nextjs_slack/Dockerfile

@@ -0,0 +1,11 @@
+FROM python:3.11-slim
+
+WORKDIR /app
+
+COPY requirements.txt /app
+
+RUN pip install -r requirements.txt
+
+COPY . /app
+
+CMD ["python", "app.py"]