Add common metatags to blog pages

[granicz]

It's always nice if blog URLs pasted to social sites render nicely. For instance, the WebSharper blog has the following metatags:

  <meta property="og:title" content="How to organize several Bolero pages" />
  <meta property="og:type" content="website" />
  <meta property="og:url" content="https://forums.websharper.com/topic/86268" />
  <meta property="og:image" content="https://forums.websharper.com/img/theader.jpg" />
  <meta property="og:description" content="What would be the best way to organize several pages that use Bolero. Should we have a shared _bin directory? " />
  <meta name="twitter:card" content="summary" />
  <meta name="twitter:site" content="@websharper" />
  <meta name="twitter:title" content="How to organize several Bolero pages" />
  <meta name="twitter:description" content="What would be the best way to organize several pages that use Bolero. Should we have a shared _bin directory? " />