ui-core: add build instructions to readme file

[turnerian2004]

Issue #89

[turnerian2004]

I struggled a lot today to build the project. There may be other commands that are better. Is there something that should be added or removed?

I could not resolve the problems below with this library. What am I doing something wrong? I tried to install the package as specified on the npm page, but I had no luck: https://www.npmjs.com/package/@osrd-project/ui-icons

[turnerian2004]

@sim51 @emersion I seem not able to request a review. Would you please review this pr? :)

[emersion]

It seems like this PR touches more than just the README - it also includes some package.json and package-lock.json changes. As said above, I don't think we need these changes.

To sum things up, IMHO npm install + npm run build + npm run storybook should be enough to get people started.

[Yohh]

@turnerian2004 that's a good point, basically we run the project with npm run start --ws (after npm install and npm run build) in order to load every workspace in the project, that's not an issue if you need to work for only one specific sub-project, but some of them depends on other ones (osrd-manchette needs osrd-spacetimechart, osrd-speedspacechart needs osrd-core, many of them needs osrd-icons...)

many changes are work-in-progress by @jacomyal , and a different process will be set very soon, but I think it's a good start!

[turnerian2004]

I'll get back later this week. I want to do a little reading up, if that's okay.

[turnerian2004]

@Yohh @emersion @clarani

Thank you for the feedback on the pr. Much appreciated :) Feel free to make any desired changes to merge the pr :)

[clarani]

LGTM, thanks !! ✅

This README really needed this improvement 🙏