Describe the bug

The documentation (under Icon Content -> Notes) states:

When providing a BootstrapVue icon name, you must ensure that you have registered the corresponding icon component (either locally to your component/page, or globally), if not using the full BootstrapVueIcons plugin.

The bold part does not seem to be the case. When registering an icon with components: { BIconBuilding } in the component where b-avatar icon="building" is used, no icon appears.

It does works when using Vue.component('BIconBuilding', BIconBuilding)

Based on what I understand about Vue component registration, I think that it may be that the docs here are incorrect.

Steps to reproduce the bug

1. Create a component that contains a b-avatar
2. Set an icon to b-avatar that is not registered
3. Import the icon and add it to the components section.
4. Observe that the icon does not appear

Expected behavior

Either the icon shows up as described in the docs when locally registered, or the docs change to specify that they must be globally registered with Vue.component.

Versions

Libraries:

• BootstrapVue: 2.16.0
• Bootstrap: 4.5.2
• Vue: 2.6.12

Environment:

• Browser: any

Demo

<template>
  <!-- does not show an icon -->
  <b-avatar
    :src="photo"
    icon="building" />
</template>

<script>
import { BIconBuilding } from 'bootstrap-vue'

export default {
  components: {
    BIconBuilding
  }
}
</script>

Additional context

Documentation link: https://bootstrap-vue.org/docs/components/avatar/#icon-content (under Notes)