feat: add xero-practicemanager-v3-1 spec

Author: Quentin Heng

manifest.json

@@ -39,6 +39,10 @@
       "path": "/xero-payroll-uk.yaml",
       "canPreview": true
     },
+    "practiceManagerV31": {
+      "path": "/xero-practicemanager-v3-1.yaml",
+      "canPreview": true
+    },
     "projects": {
       "path": "/xero-projects.yaml",
       "canPreview": true