[intercom] Lead support

[SegmentDestinationsBot]

Migrated from #33 by @Nabellaleen

In our business, we are strongly using Intercom Leads, as we are using Intercom as CRM and storing in some information about the lead experience on our funnel.

But by migrating into Segment, we are loosing this possibility, as segment only allowing to use analytics.identify on Intercom users.

Any plan for supporting Intercom Leads ?