- started about site

- mathjax is now loaded locally (only minimal defaults are deployed, only one renderer, default lang, ...)

- moved all dev dependencies into proper package.json section
- editor now uses the programming languages from backend and imports dynamically the syntax highlight file
- markdown fenced code blocks now loads dynamically the syntax highlight file

- added note for downloading all files (we now include a user id - name translation file if some names were invalid)
- removed not used typings
- fixed vulnerabilities (reported from npm)
  - bumped some versions
- made echo cross-platform
- removed marked.js from vendors

- build now uses cache busting hash (at least for the app bundle) + clears it on new builds