examples: show how to call a simple v module from ruby (#19073) (#19073)

This is a copy/adaptation of the python example (#13105)

examples/call_v_from_ruby/README.md

@@ -0,0 +1,7 @@
+A simple example to show how to call a function written in v from ruby
+
+Step 1: Compile the v code to a shared library using `v -d no_backtrace -shared test.v`
+
+Step 2: Run the ruby file using `ruby test.rb`
+
+Note: you do not need `-d no_backtrace` if you use gcc or clang .