Add PostHog as premium sponsors

[leggetter]

Raising as a Draft PR to get feedback and ensure it's okay to contribute in this way.

Description

Adds PostHog as a Premium sponsor. Sponsorship was paid on 23 September 2021.

TODOs

• add PostHog image(/docs/img/premium/posthog-readme.png)
• provide image should be added to the fund-rest-framework S3 bucket (image named posthog-130.png)
• get logo added to https://fund.django-rest-framework.org/topics/funding/#our-sponsors

[tomchristie]

Hiya Phil, fab to see you!

And yes, like this works absolutely fine for the README and homepage placements. Looks to me like it just needs the large format image, and then it's done.

The sidebar and sponsor page placements I need to do myself (They're not managed through the GitHub repo) - Once you've provided me with the promo text you'd like to appear in the sidebar placements and the 130px image then I'll get those up.

Related note to self - need to review how I'm monitoring Stripe sign-ups. Blergh. 😬

[leggetter]

Here's the 130x130 logo:

https://user-images.githubusercontent.com/65415371/135996800-d49fe024-32d9-441a-98d9-4c7596287a67.png

[leggetter]

Hey @tomchristie,

I've added the README image to this PR at 275x250 px. Also, the 130x130 px image is in the comment above.

I didn't realise we also got the sidebar promo. Great! Text...

PostHog is an open-source product analytics platform that offers a suite of tools, including funnels, heat maps, session recording and more, all in a single platform.

Thanks for your help!

[tomchristie]

Alrighty, sorted.

The homepage one will go up when we next build the docs on a release. Everything else is up now.

Thanks so much for the support! 💖

[leggetter]

Thanks again, Tom 🙌