Improve this Doc

# Error: $interpolate:reqcomma
Missing comma following MessageFormat plural/select keyword

    Expected a comma after the keyword “{0}” at line {1}, column {2} of text “{3}”

## Description

The MessageFormat syntax requires a comma following the "plural" or "select" extension keyword in the extended interpolation syntax.

For more information about the MessageFormat syntax in interpolation expressions, please refer to MessageFormat extensions section at AngularJS i18n MessageFormat