v0.2.5

Add EBC, with TV Brasil and three more channels

EBC, Brazil's public broadcaster, streams its television channels on
the web without an account. telesfor now offers four of them from a
tuner of their own at /ebc, numbered from 2001: TV Brasil, TV Brasil
Internacional, Canal Gov and Canal Educação. Canal Libras is left
out: the stream its page names answers 404.

Only TV Brasil has a guide, on its site, a day to a page. A page
gives a programme's start and, mostly, its name, so a programme runs
until the next one starts, which for the last of a day is the first
of the next. The times are Brasília's: the site does not say so, but
its mark of what is on now agrees. Where EBC lists no programme, or
leaves one unnamed, the guide has the channel's name in its place,
an hour at a time, so that Plex has something to offer on the three
channels without a guide.

The streams are at addresses that stay the same. Tuning looks at a
channel's playlists first, and tells apart a channel that is
unavailable, one that asks for a sign-in, one that EBC refuses
outside Brazil and one that is DRM-protected. The streams play
abroad today, but EBC keeps some of its pages to Brazil, so
-ebc-proxy is there should it do the same to them.

ffmpeg is handed the best quality of a channel only. Given them all,
it reads the start of each before it settles on the best, and EBC's
CDN takes seconds over a segment that nobody nearby has asked for
yet: a channel took up to fifteen seconds to start, and now takes
one to seven.

The daily check of TVP's real API now checks EBC's site and streams
as well.

- internal/provider/ebc: the provider, its tests and a live test.
- cmd/telesfor/main.go: EBC's tuner and -ebc-proxy.
- .github/workflows/live.yml: the daily check, for both providers.
- README.md, docs/usage.md, docs/development.md,
  packaging/linux/telesfor.env: EBC, its guide and its proxy.