doc(specification): add theatre script example, character name fields

doc/specifications.org

@@ -71,6 +71,9 @@ The following sections list standard objects for various use-cases.
 
 **** Theatre script
 1. Character name
+   * content - name to be displayed in dialogues
+   * =dramatis= - name to be displayed in the dramatis personae. If omitted, content is used.
+   * =description=
 2. Dialogue
 3. Stage direction
 4. Act
@@ -194,7 +197,56 @@ Both =...= and =*= mean "the preceding element is optional and may be repeated a
 # Switch to an XML-style =(name ((<property> . <value>)*) content)= schema for everything? 🤔
 # * Can't have content length in a single expression
 
+** Examples
+*** theatre script
+#+BEGIN_SRC lisp
+(strata
+ (properties
+  (version . "<major>.<minor>.<patch>")
+  (description . "The Project Gutenberg eBook, The Importance of Being Earnest, by Oscar Wilde")
+  (rights . "This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever.  You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org")
+  (title . "The Importance of Being Earnest - A Trivial Comedy for Serious People")
+  (author . "Oscar Wilde")
+  (date . "2006-08-29")
+  (language . "eng")
+  (ebook . 844)
+  (source . "1915 Methuen & Co. Ltd. edition")
+  (transcriber . "David Price")
+  (email . "ccx074@pglaf.org"))
+ (objects
+  (1 (1 (properties
+         (type . character-name)
+         (dramatis . "John Worthing, J.P."))
+        "Jack"))
+  (2 (1 (properties
+         (type . character-name))
+        "Algernon"))
+  (3 (1 (properties
+         (type . character-name)
+         (dramatis . "Rev. Canon Chasuble, D.D."))
+        "Chasuble"))
+  (4 (1 (properties
+         (type . character-name)
+         (dramatis . "Merriman, Butler"))
+        "Merriman")))
 
+ (layers
+  (<layer UID>
+          (<version> (properties
+                      (type . <layer-type>)
+                      <property>*)
+                     <content>)
+          ...)
+  ...)
+
+ (layout
+  (<version> (properties <property>*)
+             <document tree>
+             (layers <layer UID>*))
+  ...))
+#+END_SRC
+
+*** music score
 ** Future
 Scripting within a document enables many use cases, but with some prominent risks -
 1. it may use more computational resources than the user likes