[+] add comments

[ybregey]

Render DB column comments (col.comment) in the per-column annotation line, e.g.

# == Annotato Schema Info
# Table: sites
#
# Columns:
#  id          :bigint                         not null, primary key
#  location_id :bigint                         not null, comment: "External id from SomeService — NOT a FK to public.locations."
#  created_at  :timestamp(6) without time zone not null
#  updated_at  :timestamp(6) without time zone not null
#
# Indexes:
#  index_sites_on_location_id (location_id)