Making Grease pencil addon for blender 2.8

Hi,

I want to make few addons for grease pencil. Can you guys suggest me any good point from where I can start.

I downloaded vscode and blender development plugin. But I am clueless how to start coding for grease pencil.

Thanks in advance

There are some guides on how to write add-ons, for example:
https://docs.blender.org/manual/en/dev/advanced/scripting/addon_tutorial.html

writing an addon for grease pencil isn’t all that different than writing an addon for anything in Blender. Once you understand how to write one for something it applies to everything else. Check out the templates that ship with blender- there are great examples of how to do specific things, from there it’s just a matter of consulting the docs for information on whatever you’re trying to do.