[FEATURE REQUEST] Flavor support for web

### :speech_balloon: Description
I am implementing flavors for web using [this ](https://sebastien-arbogast.com/2022/05/02/multi-environment-flutter-projects-with-flavors/#Preparing_Your_Web_App) example. For flavoring my web builds I am creating one web-folder for each flavor and copy it on top of the default web folder before building my web app. Therefore I want my icons to be saved in a folder that I can specify in the config file.

For example:
```
web:
generate: true
output_path: web_prod
```

Thanks for considering this. Cheers!

### :question: Platform
Web

Start by reading the existing web icon-generation and configuration handling; the issue does not identify specific files or tests. Add support for a configurable web output_path so icons can be generated into a flavor-specific folder, and verify that the configured folder is used during web generation.

Written by the indexing model from the issue text.