refactor: outsource tsconfig to its own package

packages/tsconfig/nextjs.json

@@ -0,0 +1,21 @@
+{
+  "$schema": "https://json.schemastore.org/tsconfig",
+  "display": "Next.js",
+  "extends": "./base.json",
+  "compilerOptions": {
+    "plugins": [{ "name": "next" }],
+    "allowJs": true,
+    "declaration": false,
+    "declarationMap": false,
+    "incremental": true,
+    "jsx": "preserve",
+    "lib": ["dom", "dom.iterable", "esnext"],
+    "module": "esnext",
+    "resolveJsonModule": true,
+    "strict": true,
+    "strictNullChecks": true,
+    "target": "es5"
+  },
+  "include": ["src", "next-env.d.ts"],
+  "exclude": ["node_modules"]
+}