DOC: update sponsors to add Mistplay

[reshamas]

Issue with current documentation:

Page:
https://github.com/pymc-devs/pymc#sponsors

Add Mistplay. You can get their logo from this repo:
https://github.com/pymc-devs/pymcon_web_series_website

Idea or request for content:

No response

[Raj-Parekh24]

Hey @reshamas ,

Currently, I am working on the issue 6354. But currently, I am facing a hurdle to incorporate the changes.

To resolve the above-mentioned issue I have already set up a local development environment.

In the meantime can I take this issue for updating the documentation?

[reshamas]

@Raj-Parekh24 yes, you can take this issue.

[Raj-Parekh24]

Hi @reshamas ,

I have updated the documentation for adding the sponsor image with their homepage link.

I have raised PR #6570 for this issue.

Please review it and suggest any required changes.