readme update

Author: bcpeinhardt

README.md

@@ -26,3 +26,9 @@ ext install coder.coder-remote
 
 Alternatively, manually install the VSIX from the
 [latest release](https://github.com/coder/vscode-coder/releases/latest).
+
+#### Variables Reference
+
+Coder uses ${userHome} from VSCode's [variables reference](https://code.visualstudio.com/docs/editor/variables-reference). Use this when formatting paths in the coder extension settings rather than ~ or $HOME.
+
+Example: ${userHome}/foo/bar.baz