[Bug] Pipe tables do not render escaped code correctly

[rwrife]

Describe the bug
Pipe tables are not rendering code block regex correctly, based on the vscode, github and other markdown viewer experiences. Escaped characters are not getting escaped.

To Reproduce
Create a markdown file with this content:

| name | regex |
|-------------|---------|
| test | `^\d{3}-\d{3}-\d{3}-\d{3}$\|^\d{3}-\d{3}-\d{3}-\d{5}$` | 

Expected behavior
The regex output should not show $\| for example the correct output should look like:

Context (please complete the following information):

• OS: Windows
• Docfx version: 2.78.4

Additional context
Add any other context about the problem here.

[filzrev]

The regex output should not show $\|

It can be reproduced with Markdig without docfx.
It looks like same issue that reported at xoofx/markdig#236

TestCode

string markdown = @"
| name | regex |
|-------------|---------|
| test | `^\d{3}-\d{3}-\d{3}-\d{3}$\|^\d{3}-\d{3}-\d{3}-\d{5}$` | 
";

var pipeline = new MarkdownPipelineBuilder()
    .UsePipeTables()
    .Build();

var html =Markdown.ToHtml(markdown, pipeline);
Console.WriteLine(html);

Actual behavior

Pipe character is escaped with \ char.

Expected behavior

Raw pipe character is outputted generated html.

Example of GitHub Flavored Markdown preview

Input Markdown

| name | regex |
|-------------|---------|
| test | `^\d{3}-\d{3}-\d{3}-\d{3}$\|^\d{3}-\d{3}-\d{3}-\d{5}$` | 

HTML Preview

name	regex
test	^\d{3}-\d{3}-\d{3}-\d{3}$|^\d{3}-\d{3}-\d{3}-\d{5}$

GitHub Flavored Markdown Spec
https://github.github.com/gfm/#example-200