Doc page in REPL init script: add example/explanation of using directive for repl-init-script

[bjornregnell]

Version(s)
1.10.1

Describe the bug
The doc page on REPL init script should explain how to use this as a using directive as well. People are probably looking her to find a way how to make repl do things every time it starts...

Expected behaviour

Include this as an example in the doc-page on REPL init scripts:

//> using options --repl-init-script "import allmystuff.*" 

[bjornregnell]

See also discussion here: scala/scala3#24492 (reply in thread)