Treat a backslash escape as a markup character

[jimporter]

Description

This ensures that when using markdown-hide-markup, escape sequences are properly unescaped.

Related Issue

This resolves issue #377.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves an existing feature)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the CONTRIBUTING.md document.
• (N/A) I have updated the documentation in the README.md file if necessary.
• I have added an entry to CHANGES.md.
• I have added tests to cover my changes.
• All new and existing tests passed (using make test).

[panteleimon-a]

any updates?