Simplify README and improve build docs #35

Job	Run time
Code Analysers (-fsanitize=address -static-libasan)	1m 38s
Code Analysers (-fsanitize=undefined -static-libubsan)	1m 5s
Package for OpenWrt (mips_24kc, 22.03.3, https://downloads.openwrt.org/releases/22.03.3/targets/l...	5m 36s
Test Linux (ubuntu-20.04)	39s
Package for OpenWrt (i386_pentium4, 22.03.3, https://downloads.openwrt.org/releases/22.03.3/targe...	5m 20s
Test MacOS (macos-11)	11m 42s
Test Linux (ubuntu-22.04)	32s
Test MacOS (macos-12)	1m 6s
Package for OpenWrt (x86_64, 22.03.3, https://downloads.openwrt.org/releases/22.03.3/targets/x86/...	5m 19s
Test Windows (windows-2019)	1m 20s
Test Windows (windows-2022)	1m 33s
Package for Redhat/RPM	30s
Binaries for linux (arm-linux-gnueabi)	38s
Package for Debian/Ubuntu (amd64)	3m 12s
Binaries for linux (aarch64-linux-gnu)	33s
Package for Debian/Ubuntu (arm64)	2m 48s
Binaries for linux (i686-w64-mingw32, mingw-w64-i686)	53s
Package for Debian/Ubuntu (armhf)	2m 44s
Binaries for linux (x86_64-w64-mingw32, mingw-w64-x86-64)	1m 40s
Package for Debian/Ubuntu (i386)	1m 32s
Binaries for linux (mips-linux-gnu)	43s
Binaries for linux (mipsel-linux-gnu)	34s
Binaries for Windows (x86_64-pc-mingw64)	1m 27s
Binaries for MacOS (x86_64-apple-macos)	49s
Binaries for MacOS (universal arch)	46s
Binaries for MacOS (arm64-apple-macos)	37s
Upload Release Assets	0s
	55m 16s

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