csharp: Add support for default param references in documentation

csharp: Add support for default param references in documentation

Summary:
This also adds the information of default values in `parameter_def`.
This will help adding actual default parameter support in the C#
bindings.

Thanks to @segfaultxavi for improved formatting and escaping.

Fixes T8224

Reviewers: segfaultxavi, felipealmeida, brunobelo

Reviewed By: segfaultxavi

Subscribers: cedric, #reviewers, segfaultxavi, #committers

Tags: #efl

Maniphest Tasks: T8224

Differential Revision: https://phab.enlightenment.org/D10050