[Feature]: automatically run build before deploy in fly.io template

[CanRau]

What is the new or updated feature that you are suggesting?

Opening this issue as requested by Kent in #1015 to discuss how to proceed

Run npm run build automatically when running npm run deploy like

"deploy": "npm run build && fly deploy --remote-only"

or add it to the templates readme to the ## Deployment desction

Why should this feature be included?

So, to me it was quite confusing, that running npm run deploy wouldn't update my website 😳 I know it's kinda my fault not properly checking what the npm scripts are doing, but there's also no mention of ever running npm run build in the Readme.

Therefore I propose either adding it to the readme or running it automatically before deploy.

Personally I prefer the latter as I don't have much reason to deploy without building, but there might be other preferences I guess.
As for what other templates are doing, the Workers one builds already before deploying and others don't require builds or deploys, as far as I can tell.