🏷 (pkg/decidim) SDK types for learn step

This MR is a proposal for packages/decidim types.

What I have done:

• create generic types for buttons and texts
• export types for response (if we are in conversations, or in a section like learn).

Here an example on how it will be used, inspired by the snippet we've done.

async () => {
  const convId = "chatbotId:userId:whatever:you:want"
  const conversation = await decidim.conversation(convId)
  const introductionText = await conversation.introductionText();
  const introductionTextExample: typeof introductionText = {
    text: [
      "Welcome in the assembly Economy",
      "This assembly works in steps: ",
      "* 12/01: information",
      "* **15/02: proposal**",
      "* 17/03: priorisation",
      "* 05/04: results and decisions",
    ]
  }

  const menu = await conversation.menu()
  const menuExample: typeof menu = {
    text: [
      "You can now read informations about",
      "the assembly"
    ],
    buttons: [
      {
        section: SectionType.LEARN,
        params: {
          component_id: "1",
          component_manifest: "blogs",
          space_id: "3",
          space_manifest: "assemblies"
        },
        label: "Read __Pemba Economical Overview__"
      },
      {
        section: SectionType.VOTE,
        params: {
          component_id: "4",
          component_manifest: "proposals",
          space_id: "3",
          space_manifest: "assemblies"
        },
        label: "Propose"
      },
    ]
  }

  // Start learning.
  const textArticle = await conversation.learn.readNext({
    component_id: "1",
    component_manifest: "blogs",
    space_id: "3",
    space_manifest: "assemblies"
  });
  const textArticleExample: typeof textArticle = {
    text: [
      "Line 1",
      "Line 2"
    ],
    buttons: [
      {
        label: "Read More",
        params: {
          component_id: "1",
          component_manifest: "blogs",
          space_id: "3",
          space_manifest: "assemblies"
        },
        state: LearnState.READ_MORE
      }
    ]
  }
}