The dno dependency has no release and it is not clear how to package it

[dvzrv]

When looking into relying on system dependencies when building libossia, I noticed that https://github.com/thibaudk/dno has no release and cannot be packaged.

Currently, when wanting to use system libraries, the following triggers:

libossia/cmake/deps/dno.cmake

Lines 1 to 3 in 3327acd

	if(OSSIA_USE_SYSTEM_LIBRARIES)
	find_package(dno CONFIG GLOBAL)
	endif()

I think this wouldn't work, as upstream dno doesn't install cmake integration (or have integration for install the headers even).

[jcelerier]

@thibaudk