Use 'import type' in TypeScript examples

[skirtles-code]

This PR attempts to address the problem raised in #1616.

The TS settings currently used by npm init vue require the use of the type modifier when importing types. So the following won't work:

import { ref, Ref } from 'vue'

This could be fixed using:

import { ref, type Ref } from 'vue'

However, this won't currently work in the SFC Playground. Details at vuejs/repl#28.

The only syntax that seems to work in both cases is:

import { ref } from 'vue'
import type { Ref } from 'vue'

I'm not convinced this is ideal either. While it does work in all cases, I feel this is probably the least likely of the 3 options to be used in a real project.

In this PR I've switched the examples to use that last syntax. There aren't many examples that are affected. Once the Playground supports the second syntax I'd be inclined to switch to that instead.

[netlify]

✅ Deploy Preview for vuejs ready!

Name	Link
🔨 Latest commit	a89c9ec
🔍 Latest deploy log	https://app.netlify.com/sites/vuejs/deploys/6252d5602aeada00094b0c24
😎 Deploy Preview	https://deploy-preview-1656--vuejs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[dammy001]

LGTM 🤌🏾