Update nextra-docs-template file structure & contents to match nextra@v3

[nongrata081]

Issue:

Currently nextra-docs-template's files correspond to nextra@v2 (e.g. pages/_meta.json, next.config.js > require('nextra'), etc.), even though in package.json nextra version is latestwhich currently points to nextra@v3.0.11.

Solution:

Update the files and their contents to match nextra@v3 according to v3 migration guide

[crguezl]

@shuding

Agree with @nongrata081. Here are the implied versions:

➜  nextra-docs-template git:(main) ✗ git remote -v
origin  https://github.com/shuding/nextra-docs-template.git (fetch)
origin  https://github.com/shuding/nextra-docs-template.git (push)
➜  nextra-docs-template git:(main) ✗ git lg | head -n 2
7178f36 - (HEAD -> main, origin/main, origin/HEAD) Merge pull request #66 from EndangeredMassa/endangeredmassa/update-lockfile-version (hace 7 meses Shu Ding)
4a93f53 - update lockfile version (hace 7 meses Sean Massa)
➜  nextra-docs-template node --version
v20.5.0
➜  nextra-docs-template git:(main) ✗ npx next --version
Next.js v13.5.7
➜  nextra-docs-template git:(main) ✗ npm ls nextra
nextra-docs-template@0.0.1 /Users/casianorodriguezleon/campus-virtual/2223/learning/nextjs-learning/nextra-learning/nextra-docs-template
├─┬ nextra-theme-docs@3.1.0
│ └── nextra@3.1.0 deduped
└── nextra@3.1.0

When you run dev you get an error:

➜  nextra-docs-template npm run dev

> nextra-docs-template@0.0.1 dev
> next dev

node:internal/errors:496
    ErrorCaptureStackTrace(err);
    ^

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in /Users/casianorodriguezleon/campus-virtual/2223/learning/nextjs-learning/nextra-learning/nextra-docs-template/node_modules/nextra/package.json
    at new NodeError (node:internal/errors:405:5)
    at exportsNotFound (node:internal/modules/esm/resolve:261:10)
    at packageExportsResolve (node:internal/modules/esm/resolve:535:13)
    at resolveExports (node:internal/modules/cjs/loader:547:36)
    at Module._findPath (node:internal/modules/cjs/loader:621:31)
    at Module._resolveFilename (node:internal/modules/cjs/loader:1034:27)
    at /Users/casianorodriguezleon/campus-virtual/2223/learning/nextjs-learning/nextra-learning/nextra-docs-template/node_modules/next/dist/server/require-hook.js:54:36
    at Module._load (node:internal/modules/cjs/loader:901:27)
    at Module.require (node:internal/modules/cjs/loader:1115:19)
    at mod.require (/Users/casianorodriguezleon/campus-virtual/2223/learning/nextjs-learning/nextra-learning/nextra-docs-template/node_modules/next/dist/server/require-hook.js:64:28) {
  code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}

Node.js v20.5.0