Add MatroskaJS Chapter Codec

Rather than reinventing the wheel with a custom language, we can reuse and well-known one.

The goal of Matroska Script was to be similar to JavaScript/ECMAStrip/ActionScript.
But, in JS, integers can only use 56 bits. So not all ChapterUID (64-bit unsigned integer) can be addressed
with the current Matroska Script stable API.

Rather than adding a different GotoAndPlay that is compatible with JavaScript (using a string), we start from
scratch with ECMAScript 6th Edition (ES6).

chapter_codecs.md

@@ -72,6 +72,32 @@ The one and only command existing for the moment is `GotoAndPlay( ChapterUID );`
 same suggests, it means that, when this command is encountered, the `Matroska Player`
 **SHOULD** jump to the `Chapter` specified by the UID and play it, as long as this `Chapter` exists.
 
+## MatroskaJS
+
+This is the case when `ChapProcessCodecID` = 2. This is a script language build for
+Matroska purposes. It uses the [@!ECMAScript] 6th Edition (ES6) syntax. The commands are stored as text commands, in UTF-8.
+The syntax is C like, with commands spanned on many lines, each terminating with a semicolon ";". You can also include comments
+at the end of lines with "//" or comment many lines using "/* \*/". The scripts are stored
+in `ChapProcessData`. For the moment `ChapProcessPrivate` is not used.
+
+The Matroska Script contains the following commands.
+
+### GotoAndPlay
+
+The command is called with `GotoAndPlay( "<ChapterUID>" );`.
+
+As the same suggests, it means that, when this command is encountered, the `Matroska Player`
+**SHOULD** jump to the `Chapter` specified by the `ChapterUID` string and play it, as long as this `Chapter` exists.
+
+### LogMsg
+
+The command is called with `LogMsg( "A String" );`.
+
+The `Matroska Player` **SHOULD** send the provided message to the user debugging console, if there is one.
+In this example it would send "A String", without the double quotes, to the debugging console.
+
+
+
 ## DVD Menu
 
 This is the case when `ChapProcessCodecID` = 1. Each level of a chapter corresponds

rfc_backmatter_chapter_codecs.md

@@ -10,13 +10,13 @@
   </front>
 </reference>
 
-<reference anchor="ECMAScript" target="https://262.ecma-international.org/14.0/">
+<reference anchor="ECMAScript" target="https://262.ecma-international.org/6.0/">
   <front>
-    <title>ECMA-262 14th Edition, June 2022. ECMAScript 2023 language specification</title>
+    <title>ECMA-262 6th Edition, June 2015. ECMAScript 2015 language specification</title>
     <author>
       <organization>Ecma International</organization>
     </author>
-    <date month="June" year="2023" />
+    <date month="June" year="2015" />
   </front>
 </reference>