Unexpected behavior when pasting image into Markdown Editor #751

• BookStack Version (Found in settings, Please don't put 'latest'): 0.20.0
• PHP Version: PHP 7.0.25-0ubuntu0.16.04.1 (cli) ( NTS )
• MySQL Version: 10.1.31-MariaDB-1~xenial mariadb.org binary distribution

Expected Behavior

When I paste an image in the Markdown editor, I expect my cursor to end up at the end of the pasted text.

Current Behavior

When I paste an image into the Markdown editor, the cursor goes to the end and then jumps to the middle when the editor adds:

[domain]/uploads/images/gallery/[YYYY-DD-MMM/scaled-840-0/[filename]

The cursor ends up at the 'a' in 'scaled'.

Steps to Reproduce

Using Greenshot, take a screen grab and copy to clipboard. Then paste into the Markdown editor.