feat(vue): Add client-side helpers

[wobsoriano]

Important

🔎 Previews:

• https://clerk.com/docs/pr/1711/references/vue/use-auth
• https://clerk.com/docs/pr/1711/references/vue/use-clerk
• https://clerk.com/docs/pr/1711/references/vue/use-user
• https://clerk.com/docs/pr/1711/references/vue/use-sign-in

Explanation:

• We are launching an official Vue SDK for Clerk! 🎉
• We need to showcase how to use built-in composables (or what they call hooks in React)
• You will notice that all of the pages mirror the React client-side helpers. I thought of just adding a message somewhere saying that the Vue SDK provides equivalent functionality through composables, but created dedicated Vue pages since not all Vue developers use React

This PR:

• Adds client helpers (useAuth(), useClerk(), useUser(), useSignIn()) specific for Vue (basically a copy pasta of the React SDK client-side helpers but using Vue instead)
• You'll notice the return types look like this (Ref<boolean>), that just means the variable is a Vue ref

Checklist

• I have clicked on "Files changed" and performed a thorough self-review
• I have added the "deploy-preview" label and added the preview link(s) to this PR description
• All existing checks pass

[github-actions]

Hey, here’s your docs preview: https://clerk.com/docs/pr/1711