feature request: use spaces instead of tabs in continuation_indent

[antinomie8]

Thanks again for your work !
I use tabs for indentation. However, I would rather want the continuation_indent to insert spaces instead of tabs (kind of like UseTab: ForIndentation in clang-format: use tabs for indentation and spaces for alignment). I found that if I use a value for continuation_indent which is not divisible by my tab_width, then the remainder is filled with spaces, but I don't seem to be able to find an option to make it only use spaces.

[CppCXY]

The project is no longer actively maintained(Because I want to rewrite this project in Rust but don't have the time to actually implement it.). If you would like these feature, please submit them via a PR.