Merge pull request #29 from koboriakira/master

Add a solution 5-3-4 'extract-currency'
ありがとうございます!

Author: KenjiI

1-js/05-data-types/03-string/4-extract-currency/solution.md

@@ -1 +1,5 @@
-
+```js run
+function extractCurrencyValue(str) {
+  return +str.slice(1);
+}
+```