Reduce complexity by removing prettier formatting of outputted markdown

[bmish]

This reduces unnecessary complexity of trying to format the outputted markdown with prettier which may or may not be installed in user's repository. Instead, the user can choose to run prettier on their own after running this tool if they'd like. This puts the user more in control and avoids potential issues.

• Prettier hid potential markdown formatting issues
• Prettier's API will change between v2 and v3 (Simpler string trimming after prettier format #186 (comment))
• Even if prettier is installed, the user might not want to use it for markdown formatting
• It was difficult to test different prettier setups
• We recently added markdown-table to do the table formatting for us and it's very similar to prettier formatting

Fixes #185.
Fixes #88.