Proposal: Asset Budgets potentially w/ subtypes

### Bug Report or Feature Request (mark with an `x`)
```
- [ ] bug report -> please search issues before submitting
- [x] feature request
```

### Command (mark with an `x`)
```
- [ ] new
- [x] build
- [ ] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc
```

### Versions
Mac High Sierra

```
MacBook-Pro:~ damien$ node --version
v8.9.4
```
```
MacBook-Pro:~ damien$ npm --version
5.6.0
```

```
MacBook-Pro:daffodil damien$ ng --version

_ _ ____ _ ___
/ \ _ __ __ _ _ _| | __ _ _ __ / ___| | |_ _|
/ △ \ | '_ \ / _` | | | | |/ _` | '__| | | | | | |
/ ___ \| | | | (_| | |_| | | (_| | | | |___| |___ | |
/_/ \_\_| |_|\__, |\__,_|_|\__,_|_| \____|_____|___|
|___/

Angular CLI: 7.1.0
Node: 8.9.4
OS: darwin x64
Angular: 7.1.1
... animations, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router, service-worker

Package Version
------------------------------------------------------------
@angular-devkit/architect 0.10.7
@angular-devkit/build-angular 0.10.7
@angular-devkit/build-ng-packagr 0.10.7
@angular-devkit/build-optimizer 0.10.7
@angular-devkit/build-webpack 0.10.7
@angular-devkit/core 7.1.0
@angular-devkit/schematics 7.1.0
@angular/cdk 7.1.0
@angular/cli 7.1.0
@angular/pwa 0.11.3
@ngtools/json-schema 1.1.0
@ngtools/webpack 7.0.7
@schematics/angular 7.1.0
@schematics/update 0.11.0
ng-packagr 4.4.0
rxjs 6.3.3
typescript 3.1.6
webpack 4.19.1
```

### Repro steps
1. Have bundle with 2mb budget
2. Desire a budget that says all image assets are under 1mb.
3. Create an asset that is 1.5mb
4. Be unable to know that the asset outside of budget range as the "any" budget type will catch the bundle.

### The log given by the failure
N/A

### Desired functionality
I would like to set a budget **specifically** for image assets in my `ng build`. Ideally, I can configure this per image type (as each image type has different compressability.

e.g
```
{
...
"configurations": {
"production": {
...
budgets: [
{"type": "asset:jpg", "maximumWarning": "150kb", "maximumError": "300kb"},
{"type": "asset:svg", "maximumWarning": "15kb", "maximumError": "30kb"},
{"type": "asset:png", "maximumWarning": "150kb", "maximumError": "300kb"},
]
}
}
}
```

The use case here is automation around enforcing filesize requirements for assets to prevent absurd image sizes from being included. While `"type": "any"` meets this requirement, there are niches of asset types that should have stricter requirements (e.g. `svg`).

### Mention any other details that might be useful
I'm trying to create budgets for the assets we use on the `Daffodil` project:
https://github.com/graycoreio/daffodil

Specifically, the PR in question:
https://github.com/graycoreio/daffodil/pull/171

La richiesta riguarda i budget di ng build nella configurazione di produzione e propone i sottotipi asset:jpg, asset:svg e asset:png; non viene identificato alcun file sorgente né alcun test. Inizia tracciando la gestione dei budget esistente utilizzata da ng build, quindi verifica che gli asset che superano le dimensioni consentite attivino le soglie configurate di avviso ed errore per ogni sottotipo.

Scritto dal modello di indicizzazione a partire dal testo della issue.