/ command does not create new line, it rewrites the above or next line

[Aaron-Hu]

please note: these issue only exist on the release version yarn add rich-markdown-editor , they all works fine in the storybook demo.

1. type in some text 'this should not be heading', and then start a new line under it. In the new line type '/'
   
2. create heading, and you will see it turns the above line to heading
   

And, it also has the same issue when using / above the text

then it turns the next line to heading

ps: create list with / has the same issue

[tommoor]

Please see #427 (comment)