postcss-values-parser returns a syntax error when a negative value is
provided in a `calc` function after a CSS variable.
This is not an issue with Bootstrap itself, but a workaround to allow
projects using postcss-values-parser to keep upgrading and compiling
bootstrap
Ref: shellscape/postcss-values-parser#138, twbs/bootstrap#35033
Fix: #36851
* Add z-index for .toast-container
- Adds positioning and z-index to toast container so that it has a system-declared layer in relation to other components.
- Updates docs to use the class better
Fixes $34028
* Remove unnecessary z-index from docs examples
* Convert bulk of division to multiplication
* Use custom divide() function instead of Dart Sass math module for greater compatibility
* Apply suggestions from code review
* Fix functions