Sidebar tab API for extensions

[huchenlei]

Extensions now can call following API to register a sidebar tab.

  app.extensionManager.registerSidebarTab({
    id: "search",
    icon: "pi pi-search",
    title: "search",
    tooltip: "search",
    type: "custom",
    render: (el) => {
      el.innerHTML = "<div>Custom search tab</div>";
    },
  });

The list of supported icons can be find here: https://primevue.org/icons/#list

We will support custom icon later.