Add a compile time to webpack dev server and react-scripts

[alexnewmannn]

tested by installing react-scripts in a projet, running npm link on react-scripts and react-dev-utils from my fork, and then running npm link react-scripts and npm link react-dev-utils in my project, and running the build and dev task within.

This will show a compile time on each subsequent watch, and on build tasks as discussed in #2546

[alexnewmannn]

Will take a look at failing test over lunch, ran them locally but didnt fail, i may have ran the wrong suite. Leave that with me

EDIT: Looks like a few prs are failing because of this, not sure this is related to a code change of mine

[Timer]

Failure is not your fault, it's a Yarn bug.
Thanks for the PR!

[alexnewmannn]

@Timer Ah thats good, no worries. Let me know if any issues and I'll get em sorted tonight 👍

[gaearon]

I'm open to adding this but I would prefer it to be less obtrusive. You're going to see this a lot but it's rarely very useful. So it needs to be dimmed and put in a consistent place so it doesn't register visually unless you specifically look for it. Also worth looking at how Jest prints it for consistency.

[alexnewmannn]

@gaearon I guess theres two ways we can do this then.

We could put it at the end in parenthesis and faded (instead of in a sentence form)
Successfully Compiled (1.2s)

or we could have

Successfully Compiled

Time: 1.2s

I feel like the first may be the nicest implementation. Let me know!

[gaearon]

Can you make screenshots please?

[alexnewmannn]

@gaearon I havent implemented it yet, was just a comment based on the two ways jest implements time. Ill have a look at this weekend, possibly tonight.

[Timer]

Closing as stale.