DRAFT: docs: Add deployment action

[apertureless]

This MR will add a github action to automatically deploy the vuepress docs to github pages.

Todo

• [ ] Update action to use pnpm
• [ ] Update docs to use vuepress@next
• [ ] Update docs to current vue-chartjs version and usage
• [ ] Check out if it is possible to have the old v3 docs maybe deployed under a subdomain v3.vue-chartjs.org to preserve the old docs, as vuepress seem not to support versioning of docs.

[github-actions[bot]]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
dist/index.cjs	1.2 KB (0%)	24 ms (0%)	42 ms (+214.86% 🔺)	66 ms
dist/index.js	1.07 KB (0%)	22 ms (0%)	37 ms (+352.99% 🔺)	59 ms

[thabarbados]

@apertureless, I'm working on updating the docs now. You don't mind? I replaced vuepress with vitepress. What do you think about it?

[apertureless]

@thabarbados Ah alright! Then go ahead :D I am also fine with vitepress.

[dangreen]

done in https://github.com/apertureless/vue-chartjs/commit/7d01fd910fe0a430853a5529b34062d0fcf72dc3