Added PHP 8 into versions.xml for dom based on stubs.

[mumumu]

Generated verions.xml based on the following stubs.

• https://github.com/php/php-src/blob/PHP-8.0/ext/dom/php_dom.stub.php
• Note
  • the following methods not implemented in PHP-8.0.
    • domdocument
      • domdocument::renamenode
    • domimplementation
      • domimplementation::source_get_domimplementations
      • domimplementation::source_get_domimplementation
      • domimplementation::listitem
    • domnamednodemap
      • domnamednodemap::removenameditem
      • domnamednodemap::removenameditemns
      • domnamednodemap::setnameditem
      • domnamednodemap::setnameditemns
    • domnode
      • domnode::getfeature
      • domnode::comparedocumentposition
      • domnode::getuserdata
      • domnode::isequalnode
      • domnode::setuserdata
      • domtext::replacewholetext
  • not exist in stub file, but exists in manual, and can be used in PHP 8.0
    • domimplementation::__construct

[mumumu]

Note: We should follow new API DOMParentNode, DOMChildNode and related changes.
Anyway, I will merge this PR because unmerged versions.xml is harmful to manual readers.

• https://wiki.php.net/rfc/dom_living_standard_api
• Add new DOM Living Standard API to ext/dom php-src#4709