improve documentation

[ppKrauss]

Can I help to add some illustrations at Wiki or README? using http://www.bottlecaps.de/rr/ui and this EBNF we can to produce illustrations like json.org.

element ::= '[' tag-name ',' attributes ',' element-list ']'
  | '[' tag-name ',' attributes ']'
  | '[' tag-name ',' element-list ']'
  | '[' tag-name ']'
  | string

tag-name ::= string

attributes ::= '{' attribute-list '}' | '{' '}'

attribute-list ::= attribute ',' attribute-list | attribute

attribute ::= attribute-name ':' attribute-value

attribute-name ::= string

attribute-value ::= string | number | 'true' | 'false' | 'null'

element-list ::= element ',' element-list | element