[BUG] Editor Syntax Highlighting

[hreikin]

Desktop (please complete the following information):
OS: Tested on Windows/Linux
Python Version [e.g. 3.7]: Tested on 3.9+
Install Type [e.g. via pip, via git]: Git

Describe the bug
When using inline or fenced code blocks the editor window changes the background/text colour of the code blocks and it becomes unreadable.

Steps to reproduce the behavior:

• Start tkintermd
• Type in the syntax for an inline or fenced code block
• See the editor window change the background/text colour to not match the rest of the document.

Expected behavior A clear and concise description of what you expected to happen.
The background and text should match the style of the highlighting within the editor.