Fix incorrect hyphens in the top level readme (#545)
Fix incorrect hyphens in the top level readme (#545)

Some hyphens got replaced by special character hyphens, which cause errors when copied into a command line. Replace with the correct version.
firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk,firebase/firebase-unity-sdk