fix rtd env version and add comment on docker readme

Author: refraction-ray

docker/README.md

@@ -16,10 +16,14 @@ Run the docker container by the following command:
 ```bash
 sudo docker run -it --network host --gpus all tensorcircuit
 
-# if one also wants mount local source code, also add args `-v "$(pwd)":/app`
+# if one also wants to mount local source code, also add args `-v "$(pwd)":/app`
+
+# using tensorcircuit/tensorcircuit to run the prebuild docker image from dockerhub
 
 # for old dockerfile with no runtime env setting
 # sudo docker run -it --network host -e LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/cuda-11.0/targets/x86_64-linux/lib -e PYTHONPATH=/app -v "$(pwd)":/app  --gpus all tensorcircuit
 ```
 
 `export TF_CPP_MIN_LOG_LEVEL=3` maybe necessary since jax suprisingly frequently complain about ptxas version problem. And `export CUDA_VISIBLE_DEVICES=-1` if you want to test only on CPU.
+
+The built docker has no tensorcircuit installed but left with a tensorcircuit source code dir. So one can `python setup.py develop` to install tensorcircuit locally (in which one can also mount the tensorcircuit codebase on host) or `pip install tensorcircuit` within the running docker.

requirements/requirements-rtd.txt

@@ -13,4 +13,5 @@ ipykernel
 furo==2022.4.7
 sphinx-copybutton
 nbsphinx
-myst-parser
+myst-parser
+urllib3==1.26.15