Text files should end with a valid new line character.

More information: https://insight.symfony.com/what-we-analyse/missing_e_o_l

in docs/book/index.md, line 1 
  1. ../../README.md
    This file ends with no newline character, or with a different newline character than other files in your project. It won't render properly on a terminal, and it's considered a bad practice.
    Time to fix: about 15 minutes
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                                    Last edited  by Jurj-Bogdan