Update documentation about VRPLIB about vrplib HOT 1 CLOSED

The VRPLIB format consists of two parts: a problem specification part and a problem data part.

• The problem specification part consists of entries that are of the form <keyword> : <value>, where <keyword> denotes an alphanumerical keyword and <value> denotes alphanumerical or numerical data. Specifically, <value> is zero-dimensional data.
• The problem data part consists of data sections. Each data section starts with with the corresponding keyword in uppercase followed by _SECTION, e.g., NODE_COORD_SECTION. Each row of a section contains a sequence of alphanumerical or numerical values. The length of the section is either implicitly known (e.g., the number of customers), or up until the next section. Sections are parsed as nonzero-dimensional arrays.
• The file ends with EOF.

from vrplib.