Tui.editor: After switching to WYSIWYG and then back to Markdown mode, the newline is missing after <br> tag

[mistris]

Describe the bug

After switching to WYSIWYG and then back to Markdown mode, the newline is missing after <br>.
If you have table, <br> and after that you have h2 then after switching to WYSIWYG and then back to Markdown mode, the h2 header is inside the table.

To Reproduce

1. Use this markdown:

**Right aligned columns**

| Option | Description |
| -----: | ----------: |
| data | path to data files to supply the data that will be passed into templates. |
| engine | engine to be used for processing templates. Handlebars is the default. |
| ext | extension to be used for dest files. |
| test | [wefwef](ewf) |
<br>

## Links

1. Switch to WYSIWYG mode
2. Switch back to Markdown mode

Expected behavior

Newline after the
tag should not be removed.

Screenshots

Before switching to WYSIWYG

After switching to WYSIWYG and then back to Markdown

Environment:

• Windows 10 64-bit
• Google Chrome 83.0.4103.116
• ToastUI editor 2.1.2, 2.2.0, 2.3.0

[seonim-ryu]

@mistris When I check the issues below, it seems to be a problem using the renderer instead of the Editor.

https://github.com/nhn/tui.editor/issues/1122

This issue seems to be because parsing is broken when there is <br> in the renderer you are using. When using the renderer used in the Editor, <br> is parsed normally. I hope you can share me some code or example pages to check.

[trentmon]

@seonim-ryu just go to https://nhn.github.io/tui.editor/latest/tutorial-example01-editor-basic and insert this markdown:
111 <br> <br> <br> 222

and then switch to wysiwyg mode and back.
The code will be changed to:
111 222