Add support for multi column bullets

[0x4ym4n]

This enhancement adds multi-column bullet point support to RenderCV using LaTeX's multicol package (\usepackage{multicol}). It allows for more compact and visually appealing resume layouts by organizing bullet points into columns. This feature saves space and improves readability, especially for sections with many short points.

[sinaatalay]

Thank you for the suggestion! If we decide to do this, how would we handle an arbitrary number of bullets? Templating RenderCV is currently very easy because everything is in one column.

[0x4ym4n]

We can set a default value for the number of columns, for instance, one. If someone requires more than one column, such as three, they can manually modify this value.