ruby: 0000-fundamentals.rb: added .each_slice note into array
ruby: 0000-fundamentals.rb: added .each_slice note into array

This patch is created to add .each_slice note for array. It shows
how a larger array being sliced into multiple small arrays.

Signed-off-by: (Holloway) Chew, Kean Ho <bbd8faa40b0f348214bf4124b281a301299ba6dd@gmail.com>

josiahsoh/learning,hollowaykeanho/learning,josiahsoh/learning,josiahsoh/learning,hollowaykeanho/learning,josiahsoh/learning,hollowaykeanho/learning,hollowaykeanho/learning,josiahsoh/learning,hollowaykeanho/learning