[feat]: Create `<pf-notification-badge>` element

[zeroedin]

Create <pf-notification-badge> element

Reference: Notification badge

Notes to developer:

Prior art in <rh-badge>.

Possible API:

Default

<pf-notification-badge number="0"></pf-notification-badge>

Variants

<pf-notification-badge variant="read | unread | attention" number="0" ></pf-notification-badge>

Expanded (boolean attribute - sets aria-expanded via element internals)

<pf-notification-badge expanded number="10"></pf-notification-badge>

Icon:

<pf-notification-badge number="10" icon="bell" icon-set="patternfly"></pf-notification-badge>

Slotted Icon:

<pf-notification-badge number="10">
  <pf-icon slot="icon" icon="bell" set="patternfly"></pf-icon>
</pf-notification-badge>