Explain which pluggable transports are supported in Tor Connection

We should explain better which types of bridges are supported in Tor Connection.

Right now we have the list of default bridges and the obfs4... placeholder in the input field, but:

Not all supported pluggable transports have defaults bridges. For example, 14.5.4 supports WebTunnel bridges but don't have default WebTunnel bridges.
The email path below "Ask for a Tor bridge by email" doesn't include these indications.

What about changing the top section to:

Bridges are secret Tor relays. Use a bridge as your first Tor relay
if accessing Tor is blocked from where you are.

You can use **obfs4** and **WebTunnel** bridges in Tails.

_Learn more about Tor bridges._

We could do the same on the error screen.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information