Export @react-native/typescript-config/strict shorthand (#53564)

Summary:
Extending a tsconfig seems simpler than adding `compilerOptions` with `customConditions`.

### Before

```jsonc
{
  "extends": "react-native/typescript-config",
  "compilerOptions": {
    // ...
    "customConditions": ["react-native-strict-api", "react-native"]
  }
}
```

### After

```jsonc
{
  "extends": "react-native/typescript-config/strict"
  // ...
}
```

## Changelog:

[GENERAL] [ADDED] - Add `react-native/typescript-config/strict` export enabling the `react-native-strict-api` custom condition.

Pull Request resolved: #53564

Test Plan:
### `package.json`

```
{
  "name": "react-native-ts-test",
  "private": true,
  "version": "0.1.0",
  "scripts": {
    "build": "tsc --noEmit"
  },
  "devDependencies": {
    "react-native/typescript-config": "^0.81.1",
    "typescript": "^5.9.2",
    "jest": "^30.1.2"
  },
  "dependencies": {
    "react-native": "^0.81.1"
  }
}
```

### `tsconfig.json`

```
{
  "extends": "react-native/typescript-config/strict",
  "include": ["src/index.ts"]
}
```

### `src/index.ts`

```
import { View } from "react-native";
```

Run `npx resolution-explorer` and select "react-native from src/index.ts to node_modules/react-native/types_generated/index.d.ts" to verify the types are resolved correctly.

```
Explicitly specified module resolution kind: 'Bundler'.
Resolving in CJS mode with conditions 'import', 'types', 'react-native-strict-api'.
File '/Users/kraen.hansen/Repositories/react-native-ts-test/src/package.json' does not exist.
Found 'package.json' at '/Users/kraen.hansen/Repositories/react-native-ts-test/package.json'.
Loading module 'react-native' from 'node_modules' folder, target file types: TypeScript, JavaScript, Declaration, JSON.
Searching all ancestor node_modules directories for preferred extensions: TypeScript, Declaration.
Directory '/Users/kraen.hansen/Repositories/react-native-ts-test/src/node_modules' does not exist, skipping all lookups in it.
Found 'package.json' at '/Users/kraen.hansen/Repositories/react-native-ts-test/node_modules/react-native/package.json'.
Entering conditional exports.
Matched 'exports' condition 'react-native-strict-api'.
Using 'exports' subpath '.' with target './types_generated/index.d.ts'.
File '/Users/kraen.hansen/Repositories/react-native-ts-test/node_modules/react-native/types_generated/index.d.ts' exists - use it as a name resolution result.
'package.json' has a 'peerDependencies' field.
Resolving real path for '/Users/kraen.hansen/Repositories/react-native-ts-test/node_modules/react-native', result
'/Users/kraen.hansen/Repositories/react-native-ts-test/node_modules/react-native'.
Failed to find peerDependency 'types/react'.
Found 'package.json' at '/Users/kraen.hansen/Repositories/react-native-ts-test/node_modules/react/package.json'.
Found peerDependency 'react' with '19.1.1' version.
Resolved under condition 'react-native-strict-api'.
Exiting conditional exports.
Resolving real path for '/Users/kraen.hansen/Repositories/react-native-ts-test/node_modules/react-native/types_generated/index.d.ts', result
'/Users/kraen.hansen/Repositories/react-native-ts-test/node_modules/react-native/types_generated/index.d.ts'.
======== Module name 'react-native' was successfully resolved to
'/Users/kraen.hansen/Repositories/react-native-ts-test/node_modules/react-native/types_generated/index.d.ts' with Package ID
'react-native/types_generated/index.d.ts@0.81.1+react@19.1.1'. ========
```

Reviewed By: robhogan

Differential Revision: D82791201

Pulled By: philIip

fbshipit-source-id: f58d3b8fcf3d7f18dd29eef18a3c8c0cb57d1d78

Author: kraenhansen

packages/typescript-config/README.md

@@ -3,3 +3,26 @@
 This package provides the default `tsconfig.json` used by newly built React Native apps.
 
 This template is customized for specific versions of React Native, and should be updated in sync with the rest of your app.
+
+## Strict TypeScript API
+
+To opt into the new [strict TypeScript API](https://reactnative.dev/blog/2025/06/12/moving-towards-a-stable-javascript-api#strict-typescript-api-opt-in) you can extend from `@react-native/typescript-config/strict`
+
+```jsonc
+{
+  "extends": "@react-native/typescript-config/strict",
+  // ...
+}
+```
+
+or alternatively add the `customConditions` yourself:
+
+```jsonc
+{
+  "extends": "@react-native/typescript-config",
+  "compilerOptions": {
+    // ...
+    "customConditions": ["react-native-strict-api", "react-native"]
+  }
+}
+```

packages/typescript-config/package.json

@@ -15,5 +15,8 @@
     "react-native"
   ],
   "bugs": "https://github.com/facebook/react-native/issues",
-  "main": "tsconfig.json"
+  "exports": {
+    ".": "./tsconfig.json",
+    "./strict": "./tsconfig.strict.json"
+  }
 }

packages/typescript-config/tsconfig.strict.json

@@ -0,0 +1,8 @@
+{
+  "$schema": "https://json.schemastore.org/tsconfig",
+  "extends": "./tsconfig.json",
+  "display": "React Native (Strict)",
+  "compilerOptions": {
+    "customConditions": ["react-native-strict-api", "react-native"]
+  }
+}