add build-angular as dependency

[lehnberg]

after having installed npm and angular cli, running ng build on 3b9bd71 resulted in the following error:

$ ng build
Could not find module "@angular-devkit/build-angular" from "/Users/user/grin-web-wallet"

build-angular appears to be a newly introduced dependency in Angular 6.0, more info can be found in this StackOverflow question .

running the following command fixed it:

cpm install --save-dev @angular-devkit/build-angular

[Verrien]

@lehnberg

Thanks for the fix. This works good. Perhaps you should add this dependency?