Adding <style> to text editor markdown affects page UI

[gordlin]

Description

Adding a <style> element inside the text editor will affect the CSS of the storylines editor page.

Screenshots

Steps to reproduce

1. Go to 00000000-0000-0000-0000-000000000000
2. In any text editor, paste the following:

<style>
body {
    font-size: 48px;
}
</style>

3. Witness the font size for the storylines editor increase to 48px.

Expected behavior

UI font size should not change.

Actual behavior

UI font size changes. User may get jumpscared.

[yileifeng]

This one might need to marinate from Spencer's comment #429 (review)