Multiple prefixes

[GeiOoo]

Desciption

You can fill the commit message with endless prefixes when you trigger the action multiple times.
It would be great to avoid this behavior.

Reproduce

1. Empty commit message
2. click button to apply commit message prefix
3. repeat clicking the button multiple times
4. the commit message is filled with multiple prefixes
   

Expected behavior

The commit message prefix should only exist a single time in the commit message. Either check if the prefix exists already or clear the current commit message befor the prefix is applied.

[j0be]

I have this addressed in #27