v0.2.0-alpha.3

Inline answers of files Telegram already has, edits of inline messages,
drafts with Stop, and a cover on a video. A bot that passes a callback's
message on as a value no longer compiles: see Breaking.

Added

• Video cover and start. VideoOptions gained Cover, the picture
  clients show before the video plays, StartTimestamp and
  ShowCaptionAboveMedia. A cover is a file_id, a URL, a path on a
  self-hosted server or an upload; an upload goes as a part of its own,
  named by an attach:// reference, so a video and its cover travel in one
  sendVideo.
• Send options. CaptionOptions gained DisableNotification,
  ProtectContent and MessageEffectID, so every captioned send (photo,
  video, animation, audio, document, ephemeral or not) can go silently,
  protected, or with an effect, without a new method. Text sends still have
  none; docs/limitations.md says so.
• Cached inline results and the results button.
  InlineQueryResultCachedPhoto, InlineQueryResultCachedVideo and
  InlineQueryResultCachedMpeg4Gif send a file Telegram already has by its
  file_id, so an inline answer of past results fetches nothing.
  InlineAnswer.Button puts a button above the results that opens a Mini App
  or sends /start with a parameter. A button Telegram would refuse, and a
  cached video without the title Telegram requires, are refused before
  anything is sent.
• Edits of an inline message. EditInlineMessageText,
  EditInlineMessageMedia, EditInlineMessageCaption and
  EditInlineMessageReplyMarkup address a message sent through the bot by
  its inline_message_id. "Not modified" is success for all four. Telegram
  takes no upload in an inline edit, so EditInlineMessageMedia refuses one
  before sending.
• Drafts with Stop. SendMessageDraft, SendRichDraftHTML and
  SendRichDraftMarkdown stream a draft into a private chat, with
  DraftOptions for the topic, CanStop and KeepOnStop (Bot API 10.3). A
  press of Stop arrives as Update.StoppedMessageGeneration
  (MessageGenerationStopped: the chat, the topic and the draft id). A draft
  id of zero is refused before sending.

Breaking

• CallbackQuery.Message is a pointer, and CallbackQuery.InlineMessageID
  is new. A press on a button of an inline message has no message, and the
  zero value read as chat 0; now Message is nil there and
  InlineMessageID names the message. This breaks every bot that reads a
  callback's message. The change in each one: cq.Message.X stays as it is
  where the button is on the bot's own message, and a handler that can see
  an inline message checks cq.Message == nil first; a value passed on as
  cq.Message becomes *cq.Message.