Add profile fields and ability to update profile description/fields

[TomCasavant]

I've got this setup in my fork, I can create a pull request if you have any guidance on how you'd prefer this to look

right now I've set it up so you can change it via the account.json:

{
  "username": "tom",
  "avatar": "https://cdn.glitch.global/8eaf209c-2fa9-4353-9b99-e8d8f3a5f8d4/postmarks-logo-white-small.png?v=1693610556689",
  "displayName": "Tom's Bookmarks",
  "description": "An ActivityPub bookmarking and sharing site built with <a href='https://github.com/ckolderup/postmarks' target='_blank' rel='nofollow noopener noreferrer me'>Postmarks</a>.",
  "attachment": [
    {
      "type": "PropertyValue",
      "name": "Maintainer",
      "value": "<a href='https://tomkahe.com/@tom' target='_blank' rel='nofollow noopener noreferrer me'>@tom@tomkahe.com</a>"
    },
    {
      "type": "PropertyValue",
      "name": "Source Code",
      "value": "<a href='https://github.com/tomcasavant/tom-postmarks' target='_blank' rel='nofollow noopener noreferrer me'>https://github.com/tomcasavant/tom-postmarks</a>"
    }
  ]
}

I'm not sure if you'd want this simplified a bit or not so you don't plug-in the type for each attachment (I'm not sure what other types of attachments are possible either). And then sending an update to every server is pretty straightforward you just send UPDATE with the PERSON entity from actorJson(). I don't have this automatic yet though, I would assume we'd want some sort of button on the admin page to trigger an update?

From postmarks site:

Visual from mastodon:

[andypiper]

Love it. Would be happy to test a PR.