material-tc theme has out of place white scrollbar

[paw-lu]

Description of the problem or steps to reproduce

material-tc theme has an out of place white scrollbar.

Have added a PR to fix.

[paw-lu]

Originally thought this was a theme issue, but I seem unable to change the scrollbar color at all. Is there something I'm missing?

[dmaluka]

I see it's not implemented at all. It's pretty easy to implement it though.
I've uploaded #1840 which adds scrollbar color group.

As for the line-number.scrollbar and current-line-number.scroller color groups present in cmc-tc and cmc-16 colorschemes, they were added to the colorschemes by @GeigerCounter in #568 but apparently never implemented. I'm not sure what they were meant for and what's the difference between the two. Judging by the names, perhaps they were meant for some scrollbar embedded in the line ruler at the left edge, not for the regular scrollbar at the right edge.

[paw-lu]

Thank you so much @dmaluka !

Yeah, I couldn't figure out what scrollbar and scroller were for either 🤷‍♂️. Thanks for the PR! I'll update #1838 once it gets merged!