feat: add join function and joinable_range concept to string library#84

97gamjak merged 2 commits intodev97gamjak/mstd:devfrom

feature/MSTD-95-add-join-of-spans-to-string-library97gamjak/mstd:feature/MSTD-95-add-join-of-spans-to-string-libraryCopy head branch name to clipboard