Added proposed work-around for slack threaded messages

[adrian-andersson]

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

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

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[adrian-andersson]

This is not tested yet

[adrian-andersson]

Actually, based on discussion and feedback in the related issue: https://github.com/poshbotio/PoshBot/issues/170

Am closing as this is probably not the best solution