Update information for compiling OpenWrt on Windows 10

For Developers
1

I have tested and verified that Windows 10 v2004 with WSL v2 works great for compiling a full working version of an image from source.

2

Yep i can confirm this...
Was already working with WSLv1 but was a little slow...
With WSLv2 with ccache i can compile an image in less than 2-3 minute

3

Yes! After a make clean to rebuild the kernel using thumb2 mode, it took less than 5 minutes! Very impressive.