Format the message at the start in HTML

[jiedxu]

I used HTML format in the end, because how to use markdown v2 is not as clear.

[jiedxu]

The removed dev notes are:

1. To fix Python version:

$ pyenv local 3.8.13
$ poetry config virtualenvs.in-project true
$ poetry env use $(pyenv which python)

2. To export requirements.txt (used by Heroku) using Poetry:

$ poetry export -f requirements.txt --output requirements.txt --without-hashes