[javascript/en] use proper notation for decimals

Sorry for being late to the floating point game, but since we're getting all fussy I guess it might be better to use leading zeros for the example.

Omitting them will raise warnings in jshint/jslint and the likes: http://jslinterrors.com/a-leading-decimal-point-can-be-confused-with-a-dot-a and is usually considered bad style.