some issues about jsonl files

[sirius777coder]

Hi,

Great work. I wonder if we could use one command line to add many different fixed residues into one jsonl files. As it is a little bit of tired to generate fixed residues jsonl files for different fixed residues one by one.

[zhoubay]

Hi there,

I've made a PR (#27) probably related to your issue, please check and give me some advice!

Thank you!