(GH-811) Add support for unoppinionated variable name in folder

Previously the code folder was not aware of unoppinionated variable name
assignments.  This commit adds detection and an appropriate test.

Author: glennsarti

src/PowerShellEditorServices/Language/TokenOperations.cs

@@ -47,6 +47,11 @@ internal static FoldingReference[] FoldableRegions(
                 MatchTokenElement(tokens, TokenKind.HereStringLiteral, RegionKindNone)
             );
 
+            // Find unoppinionated variable names ${ \n \n }
+            foldableRegions.AddRange(
+                MatchTokenElement(tokens, TokenKind.Variable, RegionKindNone)
+            );
+
             // Find contiguous here strings @" -> "@
             foldableRegions.AddRange(
                 MatchTokenElement(tokens, TokenKind.HereStringExpandable, RegionKindNone)

test/PowerShellEditorServices.Test/Language/TokenOperationsTests.cs

@@ -111,7 +111,13 @@ double quoted herestrings should also fold
 # Comment Block 2
 # Comment Block 2
 $something = $true
-#endregion Comment Block 3";
+#endregion Comment Block 3
+
+# What about anonynous variable assignment
+${this
+is
+valid} = 5
+";
         private FoldingReference[] expectedAllInOneScriptFolds = {
             CreateFoldingReference(0,   0,  3, 10, "region"),
             CreateFoldingReference(1,   0,  2,  2, "comment"),
@@ -127,7 +133,8 @@ double quoted herestrings should also fold
             CreateFoldingReference(56,  7, 58,  3, null),
             CreateFoldingReference(64,  0, 65,  0, "comment"),
             CreateFoldingReference(67,  0, 71, 26, "region"),
-            CreateFoldingReference(68,  0, 69,  0, "comment")
+            CreateFoldingReference(68,  0, 69,  0, "comment"),
+            CreateFoldingReference(75,  0, 76,  6, null),
         };
 
         /// <summary>
@@ -244,6 +251,5 @@ public void LaguageServiceFindsFoldablRegionsWithSameEndToken() {
 
             AssertFoldingReferenceArrays(expectedFolds, result);
         }
-
     }
 }