docs: improve JSON Schema validation (#4077)

packages/gatsby/static/configuration/yarnrc.json

@@ -412,9 +412,12 @@
     "nodeLinker": {
       "_package": "@yarnpkg/plugin-pnp",
       "description": "Defines what linker should be used for installing Node packages (useful to enable the node-modules plugin), one of: `pnp`, `pnpm` and `node-modules`.",
+      "anyOf": [
+        { "type": "string" },
+        { "enum": ["pnp", "pnpm", "node-modules"] }
+      ],
       "type": "string",
-      "default": "pnp",
-      "examples": ["pnp", "pnpm", "node-modules"]
+      "default": "pnp"
     },
     "npmAlwaysAuth": {
       "_package": "@yarnpkg/plugin-npm",
@@ -620,8 +623,11 @@
     "pnpMode": {
       "_package": "@yarnpkg/plugin-pnp",
       "description": "If `strict` (the default), Yarn won't allow modules to require packages they don't explicitly list in their own dependencies. If `loose`, Yarn will allow access to the packages that would have been hoisted to the top-level under 1.x installs. Note that, even in loose mode, such calls are unsafe (hoisting rules aren't predictable) and should be discouraged.",
+      "anyOf": [
+        { "type": "string" },
+        { "enum": ["strict", "loose"] }
+      ],
       "type": "string",
-      "enum": ["strict", "loose"],
       "default": "strict"
     },
     "pnpShebang": {