Dark purple theme for utterances

[VatsaDev]

Hi its my first time on an open source project and I made a dark purple theme for utterances, hope you add it!

-vatsadev

[VatsaDev]

I also added my site to the utterances list

[VatsaDev]

hello????

[zsdycs]

Hi~ @VatsaDev

After reading this "PR", I have the following thoughts:

1. The "configuration-component.ts" file has not been modified. You should add options for this theme in <select id="theme" ……>……</select>.
2. What is colors.txt used for?
3. The "button.scss" code is not properly indented and should be formatted.
4. The title of this "PR" is "Dark purple theme for utterances", and the SITES.md file should not be modified.

good luck！

[zsdycs]

In addition, I did not run this code, if the renderings are attached, it will make this "PR" icing on the cake.