Rich Text Messages Update

[BenDenger]

This Autumn, slack will implement a different interface for text fields.
Formatting done by the user, like "Hello, this is bold text, this is italic" will be extracted into different elements with different types.

What problem are you trying to solve

keep up to date to upcoming changes

Current Behavior

currently, text is just received via the text property of blocks, in future, there will be a list of elements

Detailed Description

Detailed description can be found in the patchnotes
https://api.slack.com/changelog/2019-09-what-they-see-is-what-you-get-and-more-and-less