add tsconfig and package.json script for creating types files

Author: lobsterkatie

packages/gatsby/package.json

@@ -34,11 +34,12 @@
     "react": "^18.0.0"
   },
   "scripts": {
-    "build": "run-p build:cjs build:esm build:types",
+    "build": "run-p build:cjs build:esm build:types build:plugin",
     "build:cjs": "tsc -p tsconfig.cjs.json",
     "build:dev": "run-s build",
     "build:es5": "yarn build:cjs # *** backwards compatibility - remove in v7 ***",
     "build:esm": "tsc -p tsconfig.esm.json",
+    "build:plugin": "tsc -p tsconfig.plugin.json",
     "build:types": "tsc -p tsconfig.types.json",
     "build:watch": "run-p build:cjs:watch build:esm:watch build:types:watch",
     "build:cjs:watch": "tsc -p tsconfig.cjs.json --watch",

packages/gatsby/tsconfig.plugin.json

@@ -0,0 +1,17 @@
+{
+  "extends": "./tsconfig.json",
+
+  "include": ["gatsby-browser.js", "gatsby-node.js"],
+
+  "compilerOptions": {
+    // should include all types from `./tsconfig.json` plus types for all test frameworks used
+    // "types": ["node", "jest"]
+    "declaration": true,
+    "declarationMap": false,
+    "emitDeclarationOnly": true,
+    "allowJs": true,
+    "skipLibCheck": true
+
+    // other package-specific, plugin-specific options
+  }
+}