Add pseudo-element after/before handling; this is not actually used yet

during rendering anywhere.

@@ -37,7 +37,8 @@ const nthChildPos = (node, parent) => filterChildElements(parent).findIndex((chi
 
 const filterChildElementsMatcher = (context, child, parent, i) => child.type === ELEMENT_NODE
 
-type Matcher = (context, node: NodeType, parent?: NodeType, i: number, debug: number) => boolean
+type NodePosition = number | 'before' | 'after'
+type Matcher = (context, node: NodeType, parent?: NodeType, i: NodePosition, debug: number) => boolean
 type MatcherProducer = () => Matcher
 type AttrValueMatch = (string) => string
 
@@ -295,6 +296,16 @@ const compileMatcher = (ast: AST, selector: string): MatcherProducer => {
         }
       case 'universal':
         return (context, node,  parent, i, debug) => true
+      case 'pseudo-element':
+        switch (ast.name) {
+          case 'after':
+            return (context, node, parent, i, debug) => i === 'after'
+          case 'before':
+            return (context, node, parent, i, debug) => i === 'before'
+          default:
+            console.error('pseudo-class', nodeUtil.inspect({ selector, ast }, { depth: null, colors: true }))
+            throw new Error(`Unknown pseudo-class: ${ast.name}`)
+        }
       default:
         throw new Error(`Unhandled ast: ${ast.type}`)
     }