sprint 34 - czech language

updated
Update strings.js
Update CodeMirror to the latest including ES6 support
Merge pull request #6117 from adobe/rlim/codemirror-with-es6

Update CodeMirror to the latest including ES6 support.
Merge pull request #6081 from gero3/patch-1

Update strings.js
Merge pull request #6025 from kvarel/patch-11

sprint 34 - czech language