Add t.co and /cards link resolvers

For t.co links: https://t.co/.. -> nitter.net/t.co/..
For card links: https://cards.twitter.com/cards/.. -> nitter.net/cards/...

src/api/resolver.nim

@@ -0,0 +1,13 @@
+import asyncdispatch, httpclient
+
+import ".."/[formatters, types]
+
+proc resolve*(url: string; prefs: Prefs): Future[string] {.async.} =
+  let client = newAsyncHttpClient(maxRedirects=0)
+  try:
+    let resp = await client.request(url, $HttpHead)
+    result = resp.headers["location"].replaceUrl(prefs)
+  except:
+    discard
+  finally:
+    client.close()