Add an example on how to use it

examples/plugin.nim

@@ -0,0 +1,7 @@
+# Compile with: nim c --noMain --app:lib plugin.nim
+proc hello(x: int) {.exportc.} =
+  echo "Hello world, ", x
+
+proc highFive(): int {.exportc.} =
+  result = 5
+  echo "Here you go!"