Suggestions for improvements

[halirutan]

I highly appreciate this project and finally found some time to skim through your code. This PR is not meant for merging but I rather want to point out some things you probably should take a look at.

The only thing I really believe is an oversight on your part is that some of your operator= do not return the this pointer. Others are only suggestions according to clang-tidy:

• static_assert with empty string
• A lot of added explicit for one argument constructors but not for initializer_list (reference)
• noexcept for e.g. move constructors if applicable
• initialization for some uninitialized members like size_
• [[nodiscard]] to let the compiler warn the user (reference)

[njpipeorgan]

Thanks for the suggestions! They all seem good to me.