[feature] Implement custom-links

[nelson6e65]

Scopes

• Installation
• Documentation
• Template (twig, xml)
• PHP sources
• Output HTML
• Output Markdown
• Appearance
• Other

Is your feature request related to a problem? Please describe.
Difficult to add custom internal links between elements (class/members/etc).

Describe the solution you'd like
Add normalized links, so accessible by expected links.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context

• https://github.com/abernov/markdown-it-custom-header-link
• Custom header links vuejs/vuepress#679 (comment)