Embeddings, embeddings everywhere

• Fixed embedding issues when embedding blocks.
• Embeddings are now handled by Quartz Syncer instead of Quartz.
  • This behavior can be configured in the settings Quartz > Apply embeds.
• Added settings menu for Quartz Themes.
  • This currently does nothing, but will be used for managing and applying Obsidian themes to Quartz.
• Fixed some minor typos.
• Updated documentation.