Add profile-page to webfinger

http://webfinger.net/rel/profile-page is used by plugins like https://streetpass.social/ to find human readable profiles

curl --silent https://mastodon.mauve.moe/.well-known/webfinger?resource=acct:mauve@mastodon.mauve.moe | jq .

{
  "subject": "acct:mauve@mastodon.mauve.moe",
  "aliases": [
    "https://mastodon.mauve.moe/@mauve",
    "https://mastodon.mauve.moe/users/mauve"
  ],
  "links": [
    {
      "rel": "http://webfinger.net/rel/profile-page",
      "type": "text/html",
      "href": "https://mastodon.mauve.moe/@mauve"
    },
    {
      "rel": "self",
      "type": "application/activity+json",
      "href": "https://mastodon.mauve.moe/users/mauve"
    },
    {
      "rel": "http://ostatus.org/schema/1.0/subscribe",
      "template": "https://mastodon.mauve.moe/authorize_interaction?uri={uri}"
    }
  ]
}