Merge branch 'pv/spell' of https://github.com/piever/ChainRulesCore.jl into pv/spell

Author: piever

src/differentials/abstract_zero.jl

@@ -4,8 +4,8 @@
 Supertype of zero-like differentials—i.e., differentials that act like zero when
 added or multiplied to other values.
 If an AD system encounters a propagator that takes as input only subtypes of `AbstractZero`,
-then it can stop performing AD operations. All propagators are linear functions, and thus
-the final result will be zero.
+then it can stop performing AD operations.
+All propagators are linear functions, and thus the final result will be zero.
 
 All `AbstractZero` subtypes are singleton types.
 There are two of them: [`Zero()`](@ref) and [`DoesNotExist()`](@ref).