[v3 examples] add README

v3/examples/README.md

@@ -0,0 +1,18 @@
+# v3
+
+This directory is experimental. It probably won't work for you. There's no support for this directory. Dragons be here. You have been warned!
+
+The examples in this directory may or may not compile / run at any given time.  But the general method to try them out is as follows:
+
+## Running the examples
+
+    cd v3/examples/<example>
+    go mod tidy
+    go run main.go
+
+## Compiling the examples
+
+    cd v3/examples/<example>
+    go mod tidy
+    go build
+    ./<example>