docs: add tip on how to find available command ids

[CanRau]

Thanks a lot for this amazing extension, exactly what I was looking for 🥳

I might've overlooked it, but I had to search to know how to find available command ids I could use in my sequence so I thought it'd be nice to add to the readme.

What do you think?

[ryuta46]

Thank you for the great PR! I checked the way mentioned in the contents you edited. I can find all commands but I was not able to find the command id of a command in my environment. Is there a way to get the command id of a command?

[CanRau]

You're right, I clarified how to get the command id from the shortcut list

[ryuta46]

I understand. I merged your change. Thank you so much.