Add support for localization hints in schema files (#8016)

Extension/c_cpp_properties.schema.json

@@ -188,6 +188,7 @@
         "env": {
             "type": "object",
             "description": "Custom variables that can be reused anywhere in this file using the ${variable} or ${env:variable} syntax.",
+            "descriptionHint": "The word 'variable' within curly braces should also be translated.  The \"env\" should not be translated, and the punctuation (\"${:}\")  should be preserved.",
             "patternProperties": {
                 "(?!^workspaceFolder$)(?!^workspaceRoot$)(?!^workspaceFolderBasename$)(?!^default$)(^.+$)": {
                     "oneOf": [

Extension/gulpfile.js

@@ -219,8 +219,9 @@ const processJsonSchemaFiles = () => {
         };
         let descriptionCallback = (path, value, parent) => {
             let locId = filePath + "." + path;
+            let locHint = parent.descriptionHint;
             localizationJsonContents[locId] = value;
-            localizationMetadataContents.keys.push(locId);
+            localizationMetadataContents.keys.push(locHint ? { key: locId, comment: [locHint] } : locId);
             localizationMetadataContents.messages.push(value);
         };
         traverseJson(jsonTree, descriptionCallback, "");