[dreamwidth/dw-free] cddf26: Replace tint and shade with mix

[github]

Branch: refs/heads/master
Home: https://github.com/dreamwidth/dw-free
Commit: cddf26b2f4c558884454b372df311ec9b2384160
https://github.com/dreamwidth/dw-free/commit/cddf26b2f4c558884454b372df311ec9b2384160
Author: Nick Fagerlund <nick.fagerlund@gmail.com>
Date: 2020-07-08 (Wed, 08 Jul 2020)

Changed paths:
M htdocs/scss/skins/_alert-colors-dark.scss
M htdocs/scss/skins/_skin-colors.scss
M htdocs/scss/skins/celerity.scss
M htdocs/scss/skins/gradation/_gradation-base.scss

Log Message:
-----------
Replace tint and shade with mix

These functions were Compass-specific Ruby extensions to Sass. Compass is
deprecated abandonware, and using any of its gunk blocks any modernization of
the build toolchain.