Example usage does not work for add command

[nus-pe-script]

Describe the bug
As mentioned in the user guide, it gave an example of following
add n/Tutorial 3 m/CG1112 d/21-03 t/urgent.

However, this example results in an invalid command format.

To Reproduce
Steps to reproduce the behavior:

1. input add n/Tutorial 3 m/CG1112 d/21-03 t/urgent

Expected behavior
Adds a task with the name Tutorial 3, module code CG1112,
date 21-03, with the tag urgent.

Screenshots

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Reported by: @lycjackie
Severity: Medium

_{[original: nusCS2113-AY1819S2/pe-dry-run#7]}

[khairulhazril]

Fixed. Thank you!