Safari 9.0, coming in the El Capitan release, will introduce pinned tabs which will support a custom pinned-tab favicon. Example:
You can find the full docs for creating them here. If you want to add one to your RW project you can do so very easily as RW supports SVGs. Here’s how:
Create your favicon. As the docs say, it should be a full-black on transparent SVG. I’d recommend Sketch as a vector drawing tool, you can get a free trial for it here.
Drag it into the resources area in RW.
Go to the site-wide code area in your project settings and within the “Head:” section paste the following:
<link rel="mask-icon" href="%resource(website_icon.svg)%" color="#000000">
website_icon.svg should be changed to whatever you named your SVG. See the docs for info about changing it’s colour.
And that’s it
Have a good evening/day.