Various improvements/optimisation to the main script, the README and the documentation

[Antiz96]

This PR aims to add various improvements/optimisation to the main script, the README and the documentation (man page).

Main script:

• General improvements of the comments and "echoed" sentences (grammar corrections, more accurate details, better phrasing, gender neutral sentences, etc...)
• Minor code optimisations/better styling
• Added error handling when an error occurs during the removal process of the orphan package(s)

README:

• General improvements (grammar corrections, more accurate details, better phrasing, etc...)

Documentation:

• General improvements (grammar corrections, more accurate details, better phrasing, etc...)

[Antiz96]

LGTM