Support the alire package-ecosystem

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Feature description

It would be great if the [alire](https://github.com/alire-project/alire) package-ecosystem would be supported.

P.S.: Somewhen I probably would do this myself, but right now there are things having higher priority.

The issue names the Alire package ecosystem but does not mention any files, tests, or implementation entry points. Start by examining how existing package-ecosystem integrations are organized and review the linked Alire project to determine the required behavior. Done means Dependabot supports Alire as a package ecosystem and its behavior is covered by the project’s applicable tests.

Written by the indexing model from the issue text.