[BUG]: Link for "Graphol" in README.md is dead

[tillmo]

Describe the bug

The link for "Graphol" in README.md is dead

Reproduction Steps

Click on the link "Graphol" leading to http://www.diag.uniroma1.it/~graphol

Expected Result

The link should lead to an existing page.

Actual Result

404

Affected Versions

develop

Installation

None

Operating System

GNU/Linux

Operating System Version

Ubuntu 20.04

Operating System Architecture

x86_64

Log

No response