add backslashes to escape table closing

NOTE: this is my first merge request... any help appreciated. I just clicked on the 'error or improvement' merge request button.

What does this MR do?

adds \ to a |s to prevent table from closing before end of line

previously:

|  header1  |  header2  |
|  ---  |  ---  |
                 <!-- right here v -->
| some important text | `(option1|option2)`  |

the | would close the table and the other options would not be shown

url: https://docs.gitlab.com/ee/api/project_templates.html

screenshot:

What are the relevant issue numbers?

none?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated - I think?
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides