Add og:type=website

While I'm at it, add twitter tags:

<meta name="twitter:card" content="summary_large_image">
<meta property="twitter:domain" content="kana.gawa.moe">
<meta property="twitter:url" content="https://kana.gawa.moe/">
<meta name="twitter:title" content="Hello!">
<meta name="twitter:description" content="As is customary: hello, world.">
<meta name="twitter:image" content="">