feat(issue template): improve syntax for better readability and issue reporting

[SimJoSt]

These are my suggestions to make the issue templates cleaner, easier to read and improve on the ease of reporting issues.

Warn Checklist

• [ ] This changes the interface and requires a Major/Minor version change.
• [ ] I have :tophat:'d these changes by using the commands I changed by hand.
• [ ] I have added a dependency to the project.
• [ ] I have considered any potential impact on node-themekit

[tanema]

Thanks! I would love to merge this but you need to sign the CLA. Let me know when you do, it normally needs to be rerun