[WIP] Major 16 manifest

[d3m1d0v]

Description

A set of changes in a future major release

• extensions from the transformer are now connected manually
• remove addNode() and addMark() from ExtensionBuilder (wysiwyg)
  https://github.com/gravity-ui/markdown-editor/milestone/1
• extensions latex, mermaid, gpt, folding-heading, quote-link, yfm-html-block are moved to separate packages within editor's monorepo
• new serializer for wysiwyg mode (pm –> md)

Deps

• diplodoc-platform/transform@5 more info here

Other

• move yfm and additional extensions into separate extensions and npm packages within current monorepo (gravity-ui/markdown-editor-extensions)
• remove old toolbar configs, use new toolbar configuration system
• remove usage of markdown-it-attrs in YfmConfigs extension
• remove old singleton logger, rename Logger2 to Logger