Heex formatter - a Formatter for Heex templates

Im testing this in a new phoenix app and when I try

mix format lib/test_crm_web/live/customer_live/index.html.heex

I get the error:

lib/test_crm_web/live/customer_live/index.html.heex:1:1: syntax error before: '<'

I have done nothing else than generated a live resource. Is there anything I missed?