An example to show how to program ATTINY 13 AVR in C language
The bootloader used on the chip is https://github.com/MCUdude/MicroCore
Fuse can be calculated by visiting http://eleccelerator.com/fusecalc/fusecalc.php?chip=attiny13a
The process can be simplified if you are using docker by deploying docker image from https://hub.docker.com/r/lpodkalicki/avr-toolchain
You will need to have avr-gcc and avrdude installed on your system in order to compile and flash the fuses and the program to the AVR