how to compile GitHub source for installing on the router as ipk or just install from GitHub link, for example, this GitHub link
https://github.com/openwrt/packages/tree/openwrt-21.02/sound/shairplay
her is my # cat /etc/openwrt_release OUTPUT
root@OpenWrt:~# cat /etc/openwrt_release
DISTRIB_ID='OpenWrt'
DISTRIB_RELEASE='SNAPSHOT'
DISTRIB_REVISION='r0-8d5b8bf'
DISTRIB_TARGET='ipq807x/generic'
DISTRIB_ARCH='aarch64_cortex-a53'
DISTRIB_DESCRIPTION='OpenWrt SNAPSHOT r0-8d5b8bf'
DISTRIB_TAINTS='no-all'