Mention GPR support in VS Code extension walkthrough

For eng/ide/ada_language_server#1221

Author: AnthonyLeonardoGracio

integration/vscode/ada/package.json

@@ -788,14 +788,25 @@
                     {
                         "id": "als-get-stated-setting",
                         "title": "Set a project file",
-                        "description": "Set the active project file in the `ada.projectFile` setting.\n [Open Settings](command:workbench.action.openSettings)",
+                        "description": "Set the active project file in the ``ada.projectFile`` setting.\n [Open Settings](command:workbench.action.openSettings)",
                         "media": {
                             "markdown": "media/settings.md"
                         },
                         "completionEvents": [
                             "onSettingChanged:ada.projectFile"
                         ]
                     },
+                    {
+                        "id": "als-open-project-file",
+                        "title": "GPR project file support",
+                        "description": "Open the GPR project file you have specified in ``ada.projectFile`` setting. Open the ``Outline`` view to see all the entities (packages, switches...) of your GPR file.",
+                        "media": {
+                            "markdown": "media/settings.md"
+                        },
+                        "completionEvents": [
+                            "onLanguage:gpr"
+                        ]
+                    },
                     {
                         "id": "als-get-stated-debug",
                         "title": "Launch and debug",