README.md : Update with links to doc
README.md : Update with links to doc

I turned on https://codedocs.xyz/ for libiio - so start pointing people to it

Signed-off-by: Robin Getz <c66e5a86ef9317cf35cecb2ed063996b2100ed4b@analog.com>
analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio