fix: avoid breaking change in `getPathRobotConfix: incorrect robot meta tag

Fixes nuxt-modules/robots/is#137sues/137

Author: harlan-zw

Diff for: src/runtime/util.ts

@@ -191,7 +191,7 @@ export function normalizeGroup(group: RobotsGroupInput): RobotsGroupResolved {
     userAgent: group.userAgent ? asArray(group.userAgent) : ['*'],
     disallow,
     allow,
-    _indexable: disallow.includes((rule: string) => rule === '/'),
+    _indexable: !disallow.includes((rule: string) => rule === '/'),
     _rules: [
       ...disallow.map(r => ({ pattern: r, allow: false })),
       ...allow.map(r => ({ pattern: r, allow: true })),

Diff for: test/default.test.ts

@@ -37,5 +37,6 @@ describe('default', () => {
     expect((await $fetch.raw('/users/test/hidden')).headers.get('x-robots-tag')).toMatchInlineSnapshot(`"noindex, nofollow"`)
     // wildcard query
     expect((await $fetch.raw('/visible?b=foo&a=bar')).headers.get('x-robots-tag')).toMatchInlineSnapshot(`"noindex, nofollow"`)
+    expect((await $fetch.raw('/')).headers.get('x-robots-tag')).toMatchInlineSnapshot(`"index, follow, max-image-preview:large, max-snippet:-1, max-video-preview:-1"`)
   })
 })