GenerateMarkdownDoc renders Boolean default values incorrectly

[Naktibalda]

Steps to reproduce

I generated markdown of public static function addNamespace(string $prefix, string $baseDir, bool $prepend = false): void

Expected behavior

*public static* addNamespace($prefix, $baseDir, $prepend = false)

Actual behavior

*public static* addNamespace($prefix, $baseDir, $prepend = )

System Configuration

Ubuntu 20.04, PHP 8.0.21

The problem is that GenerateMarkdown uses print_r for rendering default values. print_r is completely unsuitable for printing Boolean values because it renders false as empty string and true as 1.

I think that it would be better to use var_export instead.