message: improvement(social): fully qualified url for the image
diff: <meta property="og:site_name" content="COVID-19 Mutual Aid Map - Reach4Help">
  <meta property="fb:app_id" content="1626611720838538" />
  <meta property="og:title" content="COVID-19 Mutual Aid Map - Reach4Help"/>
  - <meta property="og:image" content="%PUBLIC_URL%/banner.png"/>
  + <meta property="og:image" content="https://map.reach4help.org/banner.png"/>
  <meta property="og:description" content="Map of organizations and groups around the world offering aid and assistance to those in need during the COVID-19 crisis"/>
  <meta property="og:url" content="https://map.reach4help.org"/>
  