Packagist dependency version support

[Gummibeer]

📋 Description

A badge for Packagist to display the version constraint of a dependency. This should be similar/same to the already existing packagist/php-v badge but instead of showing hardcoded PHP version constraint it should return the version constrained for a dynamic dependency.
I'm not sure what the best URL structure would be as we would have to pass two package names to the shields.io service. First idea would be something like:

packagist/dependency-v/:user/:repo/:dependencyVendor/:dependencyRepo

🔗 Data

The data is already available in the https://github.com/badges/shields/blob/master/services/packagist/packagist-php-version.service.js - but instead of packageVersion.require.php it should use something like packageVersion.require[vendor+'/'+name].

🎤 Motivation

Some repositories want to showcase version constraints for important dependencies - for example the supported Symfony or Laravel versions.

[PaulaBarszcz]

I would like to work on this one

[chris48s]

feel free 👍