Move/strong username regex

[WillemZeiler]

PR Description:

Moved and updated the README.md
Updated the readme to be more descriptive: described the criteria the script evaluates, and added how to use the script. Moved to Regex folder.

Update and moved the Script.js
Moved to Regex folder and added comment to explain the Regex. Rest of the script is left as-is, as it was already approved.

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[kmxo]

Sounds good.