show and tell: Added a qrcode example to the Markdown Exec galery

[pawamoy]

Hey, sorry for opening an issue, discussions are not enabled 😅

Thanks a lot for this project! It's really cool.

I added an example using it in the gallery of Markdown Exec: https://pawamoy.github.io/markdown-exec/gallery/#with-qrcode.

(Markdown-Exec is an extension for Python-Markdown that allows to execute code blocks in Markdown pages 🙂)

If you scan the QRCode (or just look at the source), you'll see something nice 😜

(Feel free to close right away!)