Refactor code to use more modern C features and improve readability.

Add man page for drinfo.

drinfo.1

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+.TH DRINFO 1 "June 2024" "Version 1.0.2" "User Commands"
+.SH NAME
+drinfo \- display information about drives and their storage usage
+.SH SYNOPSIS
+.B drinfo
+.RI [ OPTION ]
+.SH DESCRIPTION
+.B drinfo
+lists all detected local and network drives and shows their storage usage graphically in the terminal.
+
+.SH OPTIONS
+.TP
+.BR -h , --help
+Show help message and exit.
+.TP
+.BR -v , --version
+Show program version and exit.
+
+.SH AUTHOR
+Lennart Martens <monkeynator78@gmail.com>
+
+.SH LICENSE
+MIT License
+
+.SH SEE ALSO
+.BR df (1),
+.BR lsblk (8)