Webssh

Fixed
* Not checking if channel is closed when error occurs while sending data.
* Unable to run on windows with Python 3.8+.

Added

* support for Python 3.8
* two more options

Changed
* Use utf-8 as the default one when the program fails to detect the default encoding of the ssh server.

Fix
* A bug of parsing url arguments when a value contains an equal sign.

Improvement
* Custom font configuration.

Add
* An option for specifying the default character encoding instead of detecting the encoding of every ssh server being connected.

Add or Update
* Upgraded to xterm.js 4.2.0
* Added support for openssh new format key
* Added support for link scope ipv6 address
* Changed default listening address

Fix
* Fixed detecting the ssh server's encoding set by the user
* Fixed showing some error messages by changing "wrong password" into "wrong passphrase"