feat: [Ast].ByType (Fixes #639)

Author: James Brundage

Types/AST/get_ByType.ps1

@@ -0,0 +1,22 @@
+<#
+.SYNOPSIS
+    Gets PowerShell AST Nodes by type
+.DESCRIPTION
+    Gets a dictionary of all nodes in a PowerShell AST beneath this point, grouped by type.
+.EXAMPLE
+    {"hello world"}.Ast.ByType
+#>
+if (-not $this.'.ByType') {
+    $ByType = [Collections.Generic.Dictionary[Type,Collections.Generic.List[PSObject]]]::new()
+    foreach ($node in $this.FindAll({$true}, $true)) {
+        $nodeType = $node.GetType()
+
+        if (-not $ByType[$nodeType]) {
+            $ByType[$nodeType] = [Collections.Generic.List[PSObject]]::new()
+        }
+        $ByType[$nodeType].Add($node)
+    }
+    Add-Member -InputObject $this -MemberType NoteProperty -Name '.ByType' -Value $ByType -Force
+}
+
+$this.'.ByType'