The + button position break when apply to bootstrap column.

[henryonsoftware]

Describe the bug
I use this packge with bootstrap, when I decrease the column from 12 to 8, the (+) button position is wrong. It isn't in the left side anymore, it was moving to cursor position.

To Reproduce
You can easy check the error by decrease screen width in the demo site https://linkesch.com/medium-editor-insert-plugin/

Device (please complete the following information):

• Device: Macbook Pro 2017
• OS: macOS
• Browser Chrome
• Version 74.0.3729.169 (Official Build) (64-bit)