Correct create svelte 4 project command (#14498)

People visiting v4.svelte.dev are interested in pre-5 svelte.
Latest version of `create-svelte` package provides no functionality to create a project (it's a notice to use v5). 
Provided materials created for v4 and earlier need not be simply thrown away, creating a pre-v5 project should still be possible.
`6.4.0` seems to be the last version of `create-svelte` package that can be used to create a v4 svelte project.

Author: parml

documentation/docs/01-getting-started/01-introduction.md

@@ -11,7 +11,7 @@ If that's not you (yet), you may prefer to visit the [interactive tutorial](/tut
 We recommend using [SvelteKit](https://kit.svelte.dev/), the official application framework from the Svelte team:
 
 ```
-npm create svelte@latest myapp
+npm create svelte@6.4.0 myapp
 cd myapp
 npm install
 npm run dev