Documentation improvements

[mispp]

I was looking for some documentation and figured that the following things do not really exist in official svelte documentation. With version 5 upcoming, it would be nice if there would be some extra guides:

• a guide how to migrate components from React to Svelte
• a guide how to make a new component which, when published, could be installed via npm
• how to properly structure an application. i dont mean routes, server and pages - those are explained, but where to put state classes and other "logic". how to model a problem and make reusable classes like "User" to be available across components for role based authorization. simple app like "todo list" should cover all of these (state management, routes, logic, component split...).
  • would be also good to split this between 1) front end only and 2) front a back end

One additional note: i went through the documentation for the upcoming v5 and i saw examples of docu that do not explicitly list which file the sample code belongs to.