Resize image

[grgprarup]

Image added with markdown syntax ![image](image-url) is not resizable and when HTML <img src="url"/> tag is used in markdown, it is not parsed by the markdown parser.

[koebel]

Not sure if this is related to the same issue about resizing: it seems that many of the header images are blurry when you watch them on a big screen. If the problem is simple that we need to upload images in higher resolution, this comment can be ignored.

maybe allow svg's?