Update the `night-mode-palette` styles to reflect the updated design
There is definitionally a visual change, but should only be for night
mode (which is currently gated behind a feature flag)
Bug: T356825
Change-Id: Iebe3b91cdf9e5e5effb2bc3ab4ff75859024056f
All colors used in Minerva are converted from Less variables
into CSS custom properties. A new file called CSSCustomProperties.less
is created in the skins.minerva.base.styles module to store
these custom properties and an ADR is provided on the rationale for
dropping support for browsers that don't support custom properties.
The new CSS custom properties follow Codex design token conventions
where possible (and noted when not).
Link colors are unique because their styles are defined in core,
so in that case the Less variables values are set to custom properties.
Those values are then fed back into MediaWiki core for core link
styling.
Also adds a temporary night-mode color palette under the
.skin-nightmode-1 class on the <html> element.
Bug: T356074
Change-Id: Ida1f14138f12bd3c600c264bde7b5100f9dbf4ff
