Add hashtag trendline support to glitch-soc flavour

Port Mastodon's hashtag stats thing to glitch-soc.
This doesn't change how hashtags are ordered, and doesn't add a trending
hashtags section, but it does change how hashtag searches are rendered,
displaying a trend line alongside each hashtag.

app/javascript/flavours/glitch/util/numbers.js

@@ -0,0 +1,10 @@
+import React, { Fragment } from 'react';
+import { FormattedNumber } from 'react-intl';
+
+export const shortNumberFormat = number => {
+  if (number < 1000) {
+    return <FormattedNumber value={number} />;
+  } else {
+    return <Fragment><FormattedNumber value={number / 1000} maximumFractionDigits={1} />K</Fragment>;
+  }
+};