added namespace

[remymumoh]

Incase you get this error
Namespace not specified. Specify a namespace in the module's build file. See https://d.android.com/r/tools/upgrade-assistant/set-namespace for information about setting the namespace

import the plugin as in pubsec.yaml

  social_share:
    git:
      url: https://github.com/remymumoh/social_share.git
      ref: master