Cannot create custom social icons with <mj-social-element>

[vai0]

Based on the latest docs for mjml 4, when creating custom icons, <mj-social-element> should not be throwing an error for attribute icon.

Observed behavior:

Fails to compile and add custom icon image URL to the social icon <img>

[ { line: 104,
    message: 'Attribute icon-color is illegal',
    tagName: 'mj-social',
    formattedMessage: 'Line 104 of /Users/admin/Projects/eloqua/emails/standard (mj-social) — Attribute icon-color is illegal' },
  { line: 109,
    message: 'Attribute icon is illegal',
    tagName: 'mj-social-element',
    formattedMessage: 'Line 109 of /Users/admin/Projects/eloqua/emails/standard (mj-social-element) — Attribute icon is illegal' },
  { line: 110,
    message: 'Attribute icon is illegal',
    tagName: 'mj-social-element',
    formattedMessage: 'Line 110 of /Users/admin/Projects/eloqua/emails/standard (mj-social-element) — Attribute icon is illegal' },
  { line: 111,
    message: 'Attribute icon is illegal',
    tagName: 'mj-social-element',
    formattedMessage: 'Line 111 of /Users/admin/Projects/eloqua/emails/standard (mj-social-element) — Attribute icon is illegal' } ] 'Line 104 of /Users/admin/Projects/eloqua/emails/standard (mj-social) — Attribute icon-color is illegal' 'Line 109 of /Users/admin/Projects/eloqua/emails/standard (mj-social-element) — Attribute icon is illegal' 'Line 110 of /Users/admin/Projects/eloqua/emails/standard (mj-social-element) — Attribute icon is illegal' 'Line 111 of /Users/admin/Projects/eloqua/emails/standard (mj-social-element) — Attribute icon is illegal'

MJML version:
4.0.0-beta.1