Fix session name label language switch + add frontend screenshot

- Store raw session name in STATE.currentSessionRawName
- Re-render session-name-display in toggleLang() with current translation
- Add frontend.png screenshot to README
- Bump 1.22.15, SW cache v46->v47

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simtrace-analyser-v46';
+const CACHE = 'simtrace-analyser-v47';
 
 const PRECACHE = [
     'index.html',