Merged PR 7944185: Add $schema to cgmanifest.json

See #23. Also adding a component registration for pyelftools, and updating the pipeline timeout for the 32-bit Linux build so that it doesn't time out.

### Why?
A JSON schema helps you to ensure that your `cgmanifest.json` file is valid. JSON schema validation is a build-in feature in most modern IDEs like Visual Studio and Visual Studio Code. Most modern IDEs also provide code-completion for JSON schemas.

Author: mlindgren

azure-pipelines.yml

@@ -292,4 +292,4 @@ jobs:
       cxx: g++
       buildType: Release
       testInPrBuild: false
-  timeoutInMinutes: 120
+  timeoutInMinutes: 240

cgmanifest.json

@@ -1,4 +1,5 @@
 {
+    "$schema": "https://json.schemastore.org/component-detection-manifest.json",
     "Registrations": [ 
         {
             "Component": { 
@@ -20,6 +21,16 @@
                 }
             },
             "DevelopmentDependency": false
+        },
+        {
+            "Component": {
+                "Type": "pip",
+                "Pip": {
+                    "Name": "pyelftools",
+                    "Version": "0.29"
+                }
+            },
+            "DevelopmentDependency": true
         }
     ]
 }