remove-baseavatar.md

@patternfly/elements
major

<pf-avatar>: Removed BaseAvatar class. Reimplement (recommended) or extend PfAvatar. Renames AvatarLoadEvent to PfAvatarLoadEvent and moves it to pf-avatar.js.

Before:

import { AvatarLoadEvent } from '@patternfly/elements/pf-avatar/BaseAvatar.js';

addEventListener('load', function(event) {
  if (event instanceof AvatarLoadEvent) {
    // ...
  }
});

After:

import { PfAvatarLoadEvent } from '@patternfly/elements/pf-avatar/pf-avatar.js';

addEventListener('load', function(event) {
  if (event instanceof PfAvatarLoadEvent) {
    // ...
  }
});