Make it so this plugin appends to the heading instead of overwriting what may have already be written underneath it

[finn-matti]

Is your feature request related to a problem? Please describe.

At the moment this plugin destructively overwrites any other content under the specified heading. I think it would be better, if it would instead (at least as an option) append completed todos.

Describe the solution you'd like
Provide an option and append new todos.

Additional context
I think this should be an option, since maybe people might want to fiddle with their completed items in things, triggering an update in Obsidian. Appending wouldn't work as well in this case. That appending only works if you do not change completed tasks and that you can't put other writing under the same heading if you overwrite should be spelled out to the user.