Conflicts with other Blender add-ons

[kudou-psoft]

https://github.com/gd3kr/BlenderGPT/blob/1ba23164974ad20d9ff1ea44d92eb636b1601a07/utilities.py#L31-L32

This code sets a custom property of "type" "content" for a PropertyGroup. However, this causes all classes that inherit from this PropertyGroup to have "type" "content" replaced with a StringProperty. Since "type" "content" is a common name and may be used for other purposes besides StringProperty, this implementation is prone to conflicts with other add-ons in Blender. Therefore, it would be necessary to fix this implementation.