Github is able to list projects dependancies for some ecosystems : Exploring the dependencies of a repository - GitHub Docs
This could be really usefull to easily track project dependancies and vulnerabilities or to track the number of project using a specific lib on github.
The platformio.ini file seems easy for github to track and they do the same thing with other ecosystems, why not platformio.
I think this features is dependent to github choice, so I make a feature request to github to support Platformio.
Perhaps, if all of us request it to github we could make it work! you can do it by sending messages here.