README: comparison with other parsers

[orangecms]

https://github.com/rs-embedded/fdt-rs

[m0veax]

https://github.com/rmsyn/devicetree-tool

[m0veax]

https://github.com/rs-embedded/fdtdump

[m0veax]

https://github.com/MoetaYuko/split-appended-dtb