Add OSUOSL to sponsors

[yol]

Logo: https://osuosl.org/about/logos/

Text:

The OSU Open Source Lab has been providing free hosting services for FOSS
projects such as Kodi since 2003. We're primarily funded through grants,
corporate sponsorships and individual contributions from the community.
Please see our website for how you can help us continue providing services
such as this.

[razzeee]

What's the sponsor level?

[razzeee]

See #688

[yol]

@keithah what do you think about just removing the sponsorship levels altogether? IMO they don't make much sense in their current form (they were based on amount of money donated and we haven't had these kinds of sponsors in a long time I guess?)

[keithah]

I think that's a good idea. Wanna make a board issue and let's discuss next meeting?

[yol]

Yep. @razzeee PR is fine for now, I will create a follow-up issue when we have sorted out the board stuff.