Docs and Features

• Doxygen friendly.
• Register a default custom allocator.
• Initialise a strbuf_t on creation from a strview_t.
• Additional number conversions with more convenient usage.
• Generic macros for many strbuf.c and strview.c functions which allow using C strings OR strview_t as arguments.
• Some renaming, as delimeters was spelled wrong.
• Simplified allocator.