Add Yocto example: Consume mosquitto via meta-conan

[uilianries]

Related to conan-io/docs#4002

This example follows the section Deploying an application to a Yocto image in the PR documentation.

Building Yocto takes several hours, so I reduced this execution to stop after fetching the mosquitto layer, so we can validate it at least.

[uilianries]

I will build locally the complete image, it takes hours and several gigabytes, so it does not fit the CI.

I'll post the build log here after it is concluded.

[uilianries]

Well, Yocto stopped my computer, and took all my disk space left, but it was doing good because stopped in the last part when building the image.

My build log is >250 MB, which is not possible to upload as an attachment in Github (max 25 MB supported).

So I uploaded it partially in my gist: https://gist.github.com/uilianries/b22bf8a3363fe624de7ffc633b60793c

It's possible to see the first part, building Mosquitto, by using Conan. It failed the first time in log due to my internet connection, but it works in the second try. After that, is all related to yocto building the full image, which takes hours to be concluded.