Reinventing the wheel: write your own printf from scratch! (Multi-character string padding)

Today, I kickstart my journey to add tons of features and tutorials on how to make various data structures and add various bits of functionality to my custom string_format function. First up: multi-character padding strings!
(Disclaimer: I'm quite a n00b, so hopefully my test cases aren't missing any glaring bugs!!!)
Test it yourself: github.com/wintcape/string_fo...
The main function is located @ test/src/main.c.
0:00 Demonstration
11:24 Header file
11:41 string_format_token_t
14:08 Global state
16:09 Validating the token
24:22 Applying the padding
29:00 TODO