I recommend reading up on them here! They're an easy way to make your messages a lot more inclusive and less easily misinterpreted!
I've created a chrome extension that allows you to quickly explain Tone Indicators without leaving your webpage.
When it's installed, all you have to do is Double-Click a tone indicator to get an explaination!
It's on the Chrome store!
If you want - you can install it from a .crx file in the latest release
Or from the unpackaged files directly Here's a guide
If you know of additional tone indicators - check out this file