## Issue
4727: Sidebar's transient scrollbar doesn't fit in the Dark Theme
## Approach
The 'webkit' API works on Chrome, but Firefox ignores it and uses it's own fancy scrollbar when 'webkit' is used (can't seem to change any properties). It's better than the current look, but still doesn't fit our theme, plus it makes the product look different on different browsers.
Firefox now supports the new 'scrollbar' API, so we can now tweak the scrollbar, but the API only provides limited attributes.
Don't wanna complicate things by using Javascript, so we'll use Firefox's limited attributes as the common denominator and just live with a plain, rectangle scroll bar BUT with better color to match the theme.
Fixed color issues that were making things hard to read:
- selected text color, including inline code.
- HTML tags
- Horizontal rule not visible in Preview mode. While at it, I changed the color in Edit mode as well as syntax highlighting.
- blockquote (was gray over gray)
Attempted to fix uneven margins between top and bottom for inline-code and codeblock. Also, removed the extra margin to make it more nice and cosy, instead of far apart.
* am I done?
* post diff
* unused selector cleanup
* missed commit
* mess with button styles
* fix flow
Co-authored-by: Jeremy Kauffman <jeremy@lbry.io>
Co-authored-by: Sean Yesmunt <sean@lbry.io>
