remove the mkdirp code in the starter scripts server:dev & build:dev

[tenretC]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Current behavior

There is an issue with the way webpack-monitor generate the folder for its reports.
I'll fix this by adding npx mkdirp reports to server:dev & build:dev scripts, but it should be removed when this issue is fixed.
NB : this only concerns the dev mode (webpack-monitor is only defined in the webpack.dev config)

Expected behavior

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Environment

Angular version: X.Y.Z
Stark version: X.Y.Z


Browser:
- [ ] Chrome (desktop) version XX
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [ ] IE version XX
- [ ] Edge version XX
 
For Tooling issues:
- Node version: XX  
- Platform:  

Others:

[dsebastien]

Did you also create an issue on webpack monitor that we could also track for a cleaner fix?

[tenretC]

Yes ;)
But thanks to Alexis I've done something much cleaner so I can close this issue
See #358

[dsebastien]

Great :)