Use venv to resolve error: externally-managed-environment (#190)

This patch try to resolve `externally-managed-environment` error by using separate venv.

```
error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
python3-xyz, where xyz is the package you are trying to
install.
    
If you wish to install a non-Debian-packaged Python package,
create a virtual environment using python3 -m venv path/to/venv.
Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
sure you have python3-full installed.
```

See also:
- https://stackoverflow.com/questions/75608323/how-do-i-solve-error-externally-managed-environment-every-time-i-use-pip-3
- https://peps.python.org/pep-0668/

Co-authored-by: 李奕鹏 <45395042+liyipeng123@users.noreply.github.com>

Dockerfile

@@ -1,6 +1,6 @@
 FROM ubuntu
 
-RUN apt update && apt install git git-lfs python3 python3-pip -y && \
+RUN apt update && apt install git git-lfs python3-full python3-pip -y && \
   echo "StrictHostKeyChecking no" >> /etc/ssh/ssh_config
 
 ADD *.sh /

entrypoint.sh

@@ -10,6 +10,8 @@ mkdir -p /root/.ssh
 echo "${INPUT_DST_KEY}" > /root/.ssh/id_rsa
 chmod 600 /root/.ssh/id_rsa
 
+python3 -m venv /hub-mirror/venv
+source /hub-mirror/venv/bin/activate
 pip3 install -r /hub-mirror/requirements.txt
 
 git lfs install