Added python validator

.github/workflows/validate_manifest.yml

@@ -1,4 +1,4 @@
-name: Validate manifest
+name: Validate manifests
 
 on:
   workflow_dispatch
@@ -10,11 +10,14 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     
-    - name: Validate Go manifest
+    - name: Validate go-versions manifest
       shell: pwsh
       run: .\packages-generation\manifest-validator.ps1 -ManifestUrl https://raw.githubusercontent.com/actions/go-versions/main/versions-manifest.json
     
-    - name: Validate Node manifest
+    - name: Validate node-versions manifest
       shell: pwsh
       run: .\packages-generation\manifest-validator.ps1 -ManifestUrl https://raw.githubusercontent.com/actions/node-versions/main/versions-manifest.json
 
+    - name: Validate python-versions manifest
+      shell: pwsh
+      run: .\packages-generation\manifest-validator.ps1 -ManifestUrl https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json