Add base inline plugin for underlined text.
Add Markdown inline plugin for underlined text.
Add HTML inline plugin for underlined text.
Add base implementation for images.
Add new test cases.
Add Markdown implementation for images.
Add HTML implementation of image plugin.
Refactor code so that other plugins can extend the image plugin and reuse its logic.
Add base plugin for links.
Add link implementation for Markdown.
Add HTML implementation of link plugin.
Update badges. At this time, it's not possible to add images inside links.