Extension:ChessBrowser/PGN schema

Description of standard

PHP parser

 * Proof of concept parser should be converted to it's own class.
 * Existing "else if" blocks can be made into sub parsers.

Developer notes

 * PHP should take import format and deliver export format.
 * JavaScript can be simplified by only accepting export format PGN. As the JavaScript is delivered by the extension, it should only take input that the PHP places on the page.
 * Parsing output can probably be done token by token without regexes
 * If extension is later expanded to resolve T239438, additional PHP function can take the export format and translate data for JavaScript

JavaScript parser
Written by Kipod, but will need modified as heavy parsing is moved to PHP. Parsing in JS may eventually be made obsolete (See T239438).