[FEAT] Use `composer.lock` to find installed Magento version in `store` mode of `get-magento-version`

# :bulb: Feature request

## Feature Name
Get Locked versions


## The Desired Behavior
In `get-magento-version` we attempt to compute the version of Magento installed. Right now, we attempt to find the version in the `composer.json`. We should instead prefer the lock file.


## Your Use Case
#126 


