fix: Do not export index.json (#508)

Although nyc does not support testing with experimental modules
nyc.config.mjs is supported in nyc 15.  This change ensures users can
`import` from @istanbuljs/nyc-config-* now that import of JSON is no
longer supported.

packages/nyc-config-babel/index.js

@@ -0,0 +1,7 @@
+'use strict';
+
+module.exports = {
+    sourceMap: false,
+    instrument: false,
+    require: ['@babel/register']
+};

packages/nyc-config-babel/package.json

@@ -2,9 +2,9 @@
   "name": "@istanbuljs/nyc-config-babel",
   "version": "3.0.0-alpha.1",
   "description": "nyc configuration that works with babel-plugin-istanbul",
-  "main": "index.json",
+  "main": "index.js",
   "files": [
-    "index.json"
+    "index.js"
   ],
   "scripts": {
     "test": "exit 0"

packages/nyc-config-typescript/index.js

@@ -0,0 +1,16 @@
+'use strict';
+
+module.exports = {
+    cache: false,
+    extension: ['.ts', '.tsx'],
+    exclude: [
+        '**/*.d.ts',
+        'coverage/**',
+        'packages/*/test/**',
+        'test/**',
+        'test{,-*}.ts',
+        '**/*{.,-}{test,spec}.ts',
+        '**/__tests__/**',
+        '**/node_modules/**'
+    ]
+};

packages/nyc-config-typescript/package.json

@@ -2,9 +2,9 @@
   "name": "@istanbuljs/nyc-config-typescript",
   "version": "1.0.0-alpha.1",
   "description": "nyc configuration that works with typescript",
-  "main": "index.json",
+  "main": "index.js",
   "files": [
-    "index.json"
+    "index.js"
   ],
   "scripts": {
     "test": "exit 0"