Added fuctionalities of detect_execpt in blug_bg

[AslanDevbrat]

I added functionality to blur only specific objects in blr_bg(). in the previous version If you give detect="Person" then your code will blur except everything except a person. But with this pull request you can pass a list of objects which is not needed to be blurred in parameter detect and also you can blur a list of specific objects with the new add parameter detect_except = [], This feature is only added to blur_bg for now.

[AslanDevbrat]

There are many aspects which can be improved in this regard. If you give me permission I will proceed

[khanfarhan10]

Please fix all merge conflicts. Also, provide documentation for the same.