Add success/error handling for invites

...in/java/com/futo/circles/extensions/FragmentExtensions.kt

...rcles/feature/group_invite/InviteMembersDialogFragment.kt

...to/circles/feature/group_invite/InviteMembersViewModel.kt

app/src/main/res/drawable/ic_error.xml

app/src/main/res/layout/error_snack_bar_view.xml

app/src/main/res/layout/success_snack_bar_view.xml

app/src/main/res/values/strings.xml