Add description to new pack files

[azzamsa]

Hi

We have this description before. I think it's better to put this description in our new monorepo pack files. The README doesn't cover as detailed as the description

<!-- Dictionary attributes:
         "nameResId" : the name of the keyboard. Should be short. Reference to a string in values.xml
         "defaultDictionaryLocale" : the ID of the keyboard's (ISO) locale, e.g., "en", "iw", "ar", "ru", etc. The dictionary should declare the same locale.
         "id" : UUID for this keyboard. Obtain from here: http://www.famkruithof.net/uuid/uuidgen
         "iconResId" : a reference to a drawable which can be used to show a flag in the notification bar.
         "layoutResId" : a reference to a keyboard layout XML. See res/xml/qwerty.xml
    -->

e.g in the new format. we don't have any information about 'physicalKeyboardMappingResId'.

I think the more description we preserved the easier newcomer to build their pack. Other alternative is to add more description to README or docs somewhere.

Thanks.

[menny]

good point. I'll update the README file