Add Piksel Core Mad

Hello Google Fonts Team!
I'm excited to submit my font family for inclusion. Please find the details below:

**Font Project Git Repo URL:**
https://github.com/fontsphere/PikselCoreMad

**Super short description of the Font Family:**
Piksel Core Mad is an experimental pixel-style display family built on a strict square grid. Includes six weights (200–700) and uppercase/lowercase letters, licensed under OFL 1.1.

**Requirements:**

By opening this issue, I confirm the project meets the following requirements:

- ✔️ The entire font project is available in a Github repository (repo) and licensed under the [OFL](https://openfontlicense.org/open-font-license-official-text/)
- ✔️ The source files are available in the repo
- ✔️ I am the sole copyright author of the entire project, or, all other copyright authors have licensed their work to me under the OFL
- ✔️ There are no "Reserved Font Names" in the OFL license information, or in the project documentation of any known upstream projects.
- ✔️ The family name is unique according to [namecheck.fontdata.com](https://namecheck.fontdata.com/)
- ✔️ The name of the font family expected to appear on app menus is clearly communicated and definitive.
- ✔️ The font supports at least the Google Fonts 'Latin Core' glyphset from [github.com/googlefonts/glyphsets](https://github.com/googlefonts/glyphsets) ([direct link](https://github.com/googlefonts/glyphsets/blob/main/data/results/txt/nice-names/GF_Latin_Core.txt))
- ✔️ The repo has the [Google Fonts preferred upstream repo structure](https://googlefonts.github.io/gf-guide/upstream.html)
- ✔️ I have read, agree with, and comply with, the full [Google Fonts contributing requirements](https://googlefonts.github.io/gf-guide/index#pre-production-getting-your-fonts-ready-for-gf)
- ✔️ I will maintain the repository and participate in the onboarding process (addressing, solving, and responding to issues, merging pull requests, etc)

**Image:**

Looking forward to your feedback!