feat: add returnValue as a Scope.presentationHint (#484)

Closes #458

changelog.md

@@ -8,6 +8,7 @@ sectionid: changelog
 
 * 1.67.x
   * Add `line`, `column`, and `source` location attributions to `EvaluateArguments`
+  * Add `returnValue` as a well-known `Scope.presentationHint`
 
 * 1.66.x
  * Add `bytes` and `asAddress` properties to the `DataBreakpointInfo` request

debugAdapterProtocol.json

@@ -3545,11 +3545,12 @@
 				"presentationHint": {
 					"type": "string",
 					"description": "A hint for how to present this scope in the UI. If this attribute is missing, the scope is shown with a generic UI.",
-					"_enum": [ "arguments", "locals", "registers" ],
+					"_enum": [ "arguments", "locals", "registers", "returnValue" ],
 					"enumDescriptions": [
 						"Scope contains method arguments.",
 						"Scope contains local variables.",
-						"Scope contains registers. Only a single `registers` scope should be returned from a `scopes` request."
+						"Scope contains registers. Only a single `registers` scope should be returned from a `scopes` request.",
+						"Scope contains a return value. A scope of this kind should have a single child variable."
 					]
 				},
 				"variablesReference": {

specification.md

@@ -3923,9 +3923,11 @@ interface Scope {
    * 'locals': Scope contains local variables.
    * 'registers': Scope contains registers. Only a single `registers` scope
    * should be returned from a `scopes` request.
+   * 'returnValue': Scope contains a return value. A scope of this kind should
+   * have a single child variable.
    * etc.
    */
-  presentationHint?: 'arguments' | 'locals' | 'registers' | string;
+  presentationHint?: 'arguments' | 'locals' | 'registers' | 'returnValue' | string;
 
   /**
    * The variables of this scope can be retrieved by passing the value of