doc: README.md example

README.md

@@ -1 +1,31 @@
-# nestlog
+# nestlog -- logging with automatic indenting according to call graph
+
+Nestlog is a lightweight header-only library for console logging.
+
+## Examples
+
+    ```
+    /* examples/ex1/ex1.cpp */
+
+    #include "nestlog/scope.hpp"
+
+    using namespace xo;
+
+    void A(int x) {
+        XO_SCOPE(log)  // i.e. xo::scope log("A");
+
+        log(":x ", x);
+    }
+
+    int
+    main(int argc, char ** argv) {
+        A(66);
+    }
+    ```
+
+  output:
+    ```
+    +A
+      :x 66
+    -A
+    ```