doc: add recursive find_or to README

README.md

@@ -835,6 +835,19 @@ const auto data = toml::parse("example.toml");
 const auto num  = toml::find_or(data, "num", 42);
 ```
 
+It works recursively if you pass several keys for subtables.
+In that case, the last argument is considered to be the optional value.
+All other arguments between `toml::value` and the optinoal value are considered as keys.
+
+```cpp
+// [fruit.physical]
+// color = "red"
+auto data  = toml::parse("fruit.toml");
+auto color = toml::find_or(data, "fruit", "physical", "color", "red");
+//                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^  ^^^^^
+//                               arguments                     optional value
+```
+
 Also, `toml::get_or` returns a default value if `toml::get<T>` failed.
 
 ```cpp