build: run build:prod on yarn prepare

[aloisklink]

📑 Summary

Adds yarn build:prod to the yarn prepare script.

For most package managers (e.g. yarn v1 and NPM), the prepare script is called automatically when installing from a local location/git url. It's not called when installing from NPM.

This is required because the source code doesn't contain the dist/mermaid.min.js file, it has to be built first.

Fixes installing mermaid via git, e.g. yarn add git+https://github.com/mermaid-js/mermaid.git

Fixes: 1549eb2

📏 Design Decisions

@sidharthv96, this undoes this line you changed in commit 1549eb2 https://github.com/mermaid-js/mermaid/blame/1549eb20dfbf0698749ab50b2cb264e63d2015b5/package.json#L44

I think you probably disabled it for testing and forgot to re-enable it when you commited, but I thought I'd @-you just in case you had a reason for disabling it.

I've used concurrently so it's a bit faster (and && is only usually supported on Windows).
I've also only enabled build:prod, since I don't think we need build:dev.

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added unit/e2e tests (if appropriate)
• 🔖 targeted develop branch

[sidharthv96]

Thanks, @aloisklink! I didn't think of that usecase. The builds were really slow and bogging down the workflow a lot.
Once #3386 is merged, it shouldn't be a problem.

[aloisklink]

The builds were really slow and bogging down the workflow a lot.

👍 It looks like by using just build:prod, GitHub Actions is slowed down by about 60/70 seconds.

We could use yarn install --no-scripts to disable this in testing, and save 60 seconds, it's but probably not worth the effort, when #3386 is soon to be merged.