Fixing more type hints

Changes

• source and source::select no longer accept generics T, instead source::select::json and source::select::transform will each accept separate generics.
  Meaning you will now type your values like so with source::select::json

  <!-- +page.svelte -->
  <script lang="ts">
    import { source } from 'sveltekit-sse'
  
    type User = {
      username: string
    }
  
    const user = 
      source('/my-event')
        .select('user')
          .json<User>()
  </script>
  
  {#if $user}
    <h3>{$user.username}</h3>
  {/if}

  And with source::select::transform

  <!-- +page.svelte -->
  <script lang="ts">
    import { source } from 'sveltekit-sse'
  
    type User = {
      username: string
    }
  
    // For the sake of brevity
    // let's suppose all the event emits 
    // is the raw name of the user
    function transformer(raw:string):User{
      return {
        username: raw
      }
    }
  
    const user = 
      source('/my-event')
        .select('user')
          .transform<User>(transformer)
  </script>
  
  {#if $user}
    <h3>{$user.username}</h3>
  {/if}