Add control over images with Markdown

Description

Images in issues are essential to illustrate a point. However

• an issue with a lot of images (in the comments too) becomes harder to read,
• it requires a lot of scrolling,
• retina images on images can become a nightmare,
• you also are more prone to miss text between two images if they are really big.

We currently have no way of controlling how these images are displayed.

Proposed solution

We could have a new option in an img markdown tag, indicating the size of the image: such as ![title|small](url.png).

We would have 4 sizes that would limit the width of the image by forcing a width: in CSS on render.

1. small: 150px wide.
2. medium: 300px wide.
3. big: 700px wide.
4. no size option: the tag as it currently works, and still the default behaviour when drag and dropping an image.

Specifications:

• When clicking on a resized image, we would toggle between the natural image size and the resized one - so anyone can see the image in its natural size in ust one click.
• The image could still be right-clicked to be opened in another tab, in order to see its natural size.