Material Design Icons is a community driven icon pack with the goal of providing the largest collection of Material Design compliant icons in an easy to use way. MDI provides several packages to facilitate a number of uses and also provides all of the icons directly on the website
I found the Material Design Icons project back in 2015 when I was playing around with a few Material Design projects and wanted more icons than the Google set provided.
I created a few issues on the GitHub repo requesting icons for my own projects and found other issues with icons I needed that had no example images to work from so decided to post some ideas. Since those first posts I have been providing feedback and moderation for the issues, providing ideas for requested icons, and I became a member of the core team.
While I haven't provided many icons to the pack (I'm still not that good with vector drawing tools), I have provided many hours of moderation as well as contributed a variety of ideas for improving our process. I designed the issue templates we use on github and reworked the labels we use to categorize our issues as well as pushing for the milestone based release system we now use for major and minor releases.