Support for Callouts

[SakuraIsayeki]

Premise

To fully support Obsidian-flavoured Markdown, we need to implement support for Callouts, as defined in #2.

Solution

Overview

Adding a new extension/converter to the current Markdig rendering pipeline solutions this issue in the best manner possible.

Requirements

• Callouts should follow the exact specification as defined in Obsidian's documentation.
• Support for callout icons should be left up to the user to toggle and switch, from a list of well-known providers (Bootstrap Icons, Font Awesome, etc)
• Support for Bootstrap being contingent for now to this feature (using their Alerts), this feature is dependent on usage of Bootstrap, and should be reflected and guarded as such in the pipeline builder.

[SakuraIsayeki]

Update

Support for GitHub's equivalent of Callouts was implemented within Markdig v0.36 (see: xoofx/markdig#776). However the supported format is far less permissive than Obsidian's variant.

To support all features, a fork of the original extension will be needed.