Need to better emphasize *optional* content

[jonfroehlich]

From the onset of creating this website, I wanted to include some optional "info boxes" that allow extra curious or more advanced students to dive deeper into a concept or area but that is optional.

Currently, the optional content isn't nearly as obvious as it needs to be. Liang said this too.

I know this. I tried for an hour or two to address this but couldn't figure it out (I'm still learning Jekyll, Kramdown, and scss). One of the Jekyll templates I considered has great support for differently styled infoboxes, like this (but I just don't know how to get this to work with my template, which is called "Just the Docs"). Here's a screenshot of the minimal mistakes info boxes:

[jonfroehlich]

Here's another great rendering of this from: https://lastminuteengineers.com/esp32-arduino-ide-tutorial/