Simplified & Updated

This release:

• [BREAKING] Removes support for RELEASE_ env vars in favor of explicitly passed ${{ env.????? }}
• Adds support for multiline body:

   with:
   	body: |
   		This
   		now
   		
   		works!

• Adds a two-stage release (only published if all assets uploaded successfully)
• Updates Alpine to 3.11
• Removes unnecessary { & } from code
• Various docs, and variables name changes