Add explicit package manager

Author: Michelle Hertzfeld

package.json

@@ -16,6 +16,7 @@
   "version": "0.4.4",
   "description": "Geospatial catalog explorer based on TerriaJS.",
   "license": "Apache-2.0",
+  "packageManager": "yarn@1.22.22",
   "engines": {
     "node": ">= 20.0.0"
   },