Update Ring-like table in Algebra for Semifield added in typelevel#3979

xref typelevel#3979 (comment)

Author: benhutchison

docs/algebra.md

@@ -55,9 +55,10 @@ All ring-like structures are associative for both `+` and `*`, have commutative
 |CommutativeRig      |             |       ✓|                 |               ✓|
 |Ring                |            ✓|       ✓|                 |                |
 |CommutativeRing     |            ✓|       ✓|                 |               ✓|
+|Semifield           |             |       ✓|                ✓|                |
+|CommutativeSemifield|             |       ✓|                ✓|               ✓|
 |Field               |            ✓|       ✓|                ✓|               ✓|
 
-With the exception of `CommutativeRig` and `Rng`, every lower structure is also an instance of the structures above it. For example, every `Ring` is a `Rig`, every `Field` is a `CommutativeRing`, and so on.
 
 (For a description of what the terminology in each column means, see [§algebraic properties and terminology](#algebraic-properties-and-terminology).)