[RFC] Give unique prompt symbol (>>>) to Nim

[AndreiRegiani]

Whether to keep >>> or come up with something unique for Nim? The issue was raised in the Telegram group, causing confusion when comparing Python and Nim code, copying & pasting from REPL.

Suggested:

• Nim>
• nim>
• nim =}>

[timotheecour]

inim> echo 1+1

TODO:

• we could have good defaults, and furthermore, could be customizable by user, via a proc that gets called each time prompt is displayed (just as zsh is).
  So allow user to pass an arbitrary lambda:

# could be (re-)defined at runtime via, say, an import
# defines proc prompt():string = ...
import my_shell_config
# calls prompt() each time the prompt is drawn

=> user can make prompt colored, add a timestamp, duration of last command, number of such prompts etc

[AndreiRegiani]

• v0.3.1 changed prompt symbol to inim>