Add commented `cudatoolkit` install commands in Dockerfile

Dockerfile

@@ -4,6 +4,11 @@ COPY apt.txt .
 RUN apt -qq update && apt -qq install -y `cat apt.txt` \
  && rm -rf /var/cache/*
 
+# Uncomment the lines to install required CUDA toolkit
+# RUN conda install -y cudatoolkit=10.1
+# RUN conda install -y cudatoolkit=10.2
+# RUN conda install -y cudatoolkit=11.3
+
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt