Misc tasks

[matu3ba]

• 1. gcc -O3, clang and tcc are not tested
• 2. you could also use address sanitizer and ub sanitizer (although I would expect they dont find anything)
• 3. add example usage for multiple types in the README
• 4. Did you consider using uint8_t instead of int ?
• 5. create a license or SPDX header.