Add specialties/skills to profiles

A number of years ago, RnD started asking people for their specialties and skills so that members could have an easier time finding people who could help them with a specific area (such as FreeIPA, NodeJS, Kubernetes, ESP32, RHEL, AC circuits, etc).

It would be beneficial to be able to see these skills in profiles, and perhaps even make them search-able.

未指定任何文件、测试或入口点。首先定位个人资料字段的存储和渲染方式，然后确定显示和搜索专长与技能的预期范围。完成意味着需求已达成一致，并且技能在个人资料中可见；如果搜索行为仍在范围内，则需定义该行为。

由索引模型根据 Issue 内容生成。