Add new parser, validator to tools page

[tychonievich]

A validating parser (and generator/serializer, but we don't have a section for those) and another validator that uses the parser.

Parser: https://github.com/gedcom7code/js-gedcom

Validator: https://gedcom7code.github.io/js-gedcom/

[dthaler]

Merging per steering committee agreement 19 October 2023