Add "powered by matrix" logo

[ShadowJonathan]

In the same vein of the "made for matrix" badge, i think a "Powered by Matrix" badge would also be really helpful to use.

Reasoning

"Powered by" is different than "Made for", with the latter implying that a particular solution was made to hook into an existing matrix ecosystem, while the former implies that it utilizes the protocol for it's own usecase, potentially adding more to the ecosystem.

To put it another way; "Made for" implies one's drive to make it was matrix specifically, while "Powered by" implies one's drive is external, but matrix helped them get there, using it as a platform.