Line breaks don't work inside `<pre>` tags in rich text widget

## To Reproduce

Step by step instructions to reproduce the behavior:

1. Add a new rich text widget
2. Select a custom `

` style or create one using the Markdown shortcut ```

3. Press ⇧ + ⏎

4. A new paragraph is created instead of a line break


## Expected behavior

A new line break should be created inside the same `
` element.


## Describe the bug

Line breaks work fine inside `
` tags using ⇧ + ⏎ but when inside `
` tags, it creates a new paragraph.


## Details

**Version of Node.js:**

16.20.1

**Server Operating System:**

Linux

**Additional context:**

The bug is present in all browsers.

**Screenshots**

No file or test is named in the issue. Start by locating the rich text widget's handling of Shift+Enter and its special handling for pre elements, then reproduce the steps in a browser. Done means Shift+Enter creates a line break inside the same pre element rather than a new paragraph.

Written by the indexing model from the issue text.