Add PyPy as primary suggestion for .py file while submitting.

[blueedgetechno]

Add a choice action b/w python and PyPy or a one-time selection which can be manually changed later.
Because PyPy proves to be much faster and helpful during cp than Python.

Also, add a password masking functionality while login with the console.

[kmyk]

oj s --guess-python-interpreter pypy main.py will work. Please use this.
If you feel this is too long, you can add alias like alias oj-s-pypy='oj s --guess-python-interpreter pypy' for your shell.

Or, if many users demands, I'll add for a shortcut option (e.g. --pypy) or a guessing feature from the shebang (i.e. strings something like #!/usr/bin/env pypy3).

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(for the problem of a password masking, go #761)