Description

Added new bundled themes and renamed each theme to the human readable name and use the new "cethemes" file extension.

Bundled themes are as follows:

• Basic
• Civic
• Classic (Dark)
• Classic (Light)
• Default (Dark)
• Default (Light)
• Dusk
• GitHub (Dark)
• GitHub (Light)
• High Contrast (Dark)
• High Contrast (Light)
• Low Key
• Midnight
• Presentation (Dark)
• Presentation (Light)
• Solarized (Dark)
• Solarized (Light)
• Sunset

Checklist

• Add new themes
• Rename each theme to human readable name and to use new "cetheme" extension
• Modify code to read files with new "cetheme" file extension
• I read and understood thecontributing guide as well as thecode of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots