Add releng documentation
Add releng documentation

A reminder for the steps to be taken for a release.

Change-Id: Ie728ccaf913f9f405a9c6fe351a5e5e3e1134f87

pimaxdev/tabris,softnep0531/tabrisjs,eclipsesource/tabris-js,softnep0531/tabrisjs,eclipsesource/tabris-js,mkostikov/tabris-js,moham3d/tabris-js,eclipsesource/tabris-js,mkostikov/tabris-js,pimaxdev/tabris,moham3d/tabris-js