Add exampleSite readme

exampleSite/README.md

@@ -0,0 +1,15 @@
+# Paige example site
+
+If you move this directory out of its parent directory,
+you must remove this line from the file go.mod:
+
+```
+replace github.com/willfaught/paige => ../
+```
+
+and then run this command:
+
+```
+$ cd exampleSite
+$ go get github.com/willfaught/paige@latest
+```