Fix React extern file to allow children as arguments, not only as array.

JSX renders children as arguments, not as array.
Release v5.1.2
Simplify basic React demo.
Release v5.1.3
Merge branch 'master' of https://github.com/steida/este-library

# By Daniel Steigerwald
# Via Daniel Steigerwald
* 'master' of https://github.com/steida/este-library:
  Release v5.1.3
  Simplify basic React demo.
  Release v5.1.2
  Fix React extern file to allow children as arguments, not only as array.