Add note that `/ext/bin/init.sh` is sourced when launching terminals on CoCalc but not on ssh.

[mforbes]

Please describe which files are used to provision the terminal environment on CoCalc and how this differs when ssh'ing into the project.

• https://doc.cocalc.com/terminal.html
• https://doc.cocalc.com/account/ssh.html

Specifically reference that /ext/bin/init.sh is sourced when using the UI, but not when logging in with ssh.

Some other ideas:

• Perhaps when connecting by ssh, a note could be displayed with the banner pointing /ext/bin/init.sh.
• Optionally, one might source this in ~/.bashrc, but this could break things so maybe it is not ideal.

[novoselt]

@haraldschilly Any comments on what is the desired and actual behaviour? I.e. what has to be documented and what has to be changed, if anything?