docs: add soapbox docs in README

README.md

@@ -2,6 +2,8 @@
 
 **Soapbox** is customizable open-source software that puts the power of social media in the hands of the people. Feature-rich and hyper-focused on providing a user experience to rival Big Tech, Soapbox is already home to some of the biggest alternative social platforms.
 
+For more info see: https://docs.soapbox.pub/soapbox/
+
 # On The Fediverse
 
 You may have heard of **Mastodon**. Soapbox builds upon what Mastodon made great to make something even better.