README: add info on Alpine runtime error (#20)

* README: add info on Alpine runtime error

Add info on readme to help with the libstdc++ load error

* README: simplify libstdc++ fix note

README.md

@@ -26,6 +26,7 @@ setting metadata into MPEG-4 files, in particular, iTunes-style metadata.
 
 * Navigate to the [latest release](https://github.com/wez/atomicparsley/releases/latest)
 * Download the `AtomicParsleyAlpine.zip` file and extract `AtomicParsley`
+* And finally `apk add libstdc++`
 
 ### Building from Source