Add Open Horizon to Landscape

[bprestonlf]

Logo = https://github.com/lf-edge/artwork/blob/master/openhorizon/horizontal/color/openhorizon-horizontal-color.svg

Website = https://www.lfedge.org/projects-old/openhorizon/

GitHub = https://github.com/open-horizon/

[ninjaginja]

@bprestonlf Do you feel that Platforms > IoT-Focused is the most appropriate category for this listing?

[ninjaginja]

Comment from Joe Pearson in regards to category:

Options that spring to mind in order of preference for Platform sub-categories:

1. Application & ML Model Delivery (wordy but descriptive, maybe too specific)
2. Application & Asset Distribution

If we were to create a sub-category like one of those, both Open Horizon and KubeFlow could be placed into it, off the top of my head.

[bprestonlf]

Application & Model Delivery