{{mobiledoc-editor}} includes non-functioning pull-quote toggle

[sdhull]

Was playing with the addon today and had what I thought was a pretty vanilla template:

  {{#mobiledoc-editor mobiledoc=properties.mobiledoc on-change=(action 'updateDoc') as |editor|}}
    {{mobiledoc-toolbar editor=editor}}
  {{/mobiledoc-editor}}

Everything worked great except the pull-quote button, which throws a MobileDocError with a message "Cannot set section tagName to pull-quote". Seems to be something about isValidTagName not being defined?

Not a big deal but should probably make vanilla use-case 100% functional. If you point me in the right direction I can take a crack at it