Using hexo.render.renderSync, Tag Plugins are not resolved

## Check List

- [x] I have already read [Docs page](https://hexo.io/docs/) & [Troubleshooting page](https://hexo.io/docs/troubleshooting)
- [x] I have already searched existing issues and they are not help to me
- [ ] I examined error or warning messages and it's difficult to solve
- [x] Using [the latest](https://github.com/hexojs/hexo/releases) version of Hexo (run `hexo version` to check)
- [x] Node.js is higher than [minimum required version](https://hexo.io/docs/#Minimum-required-Node-js-version)

## Question

I have created a generator, which loads extra Markdown content while processing. Beside parsing the Frontmatter, it renders the content with ``renderSync``:

```
...
const md = fs.readFileSync(mdSource);
data = front.parse(md);
data.content = hexo.render.renderSync({ text: data._content, engine: 'markdown' });
...
```

Works like charm ... but tag plugins contained in the content (which are working properly in pages/posts) are not resolved.

Code: [https://github.com/kristofzerbe/hexo-generator-anything/blob/main/lib/generator.js](https://github.com/kristofzerbe/hexo-generator-anything/blob/main/lib/generator.js)

## Environment & Settings

**Node.js & npm version**

```
Node: v12.16.3
NPM: 6.14.4
```

**Hexo and Plugin version(`npm ls --depth 0`)**

```
+-- hexo@5.4.0
+-- hexo-asset-link@2.1.0
+-- hexo-browsersync@0.3.0
+-- hexo-cli@4.2.0
+-- hexo-feed@1.1.0
+-- hexo-fontawesome@2.2.1
+-- hexo-front-matter@2.0.0
+-- hexo-fs@3.1.0
+-- hexo-generator-alias@1.0.0
+-- hexo-generator-anything@1.0.4
+-- hexo-generator-archive@1.0.0
+-- hexo-generator-category@1.0.0
+-- hexo-generator-copy@0.1.0
+-- hexo-generator-index@2.0.0
+-- hexo-generator-json-content@4.2.3
+-- hexo-generator-search@2.4.2
+-- hexo-generator-sitemap@2.1.0
+-- hexo-generator-tag@1.0.0
+-- hexo-hide-posts@0.1.1
+-- hexo-pwa@0.1.3
+-- hexo-renderer-ejs@1.0.0
+-- hexo-renderer-marked@4.0.0
+-- hexo-renderer-stylus@2.0.1
+-- hexo-server@2.0.0
```

**Your package.json `package.json`**

```
{
"name": "hexo-site",
"version": "0.0.0",
"private": true,
"hexo": {
"version": "5.4.0"
},
"dependencies": {
"hexo": "^5.4.0",
"hexo-asset-link": "^2.1.0",
"hexo-browsersync": "^0.3.0",
"hexo-fontawesome": "^2.2.1",
"hexo-generator-alias": "^1.0.0",
"hexo-generator-anything": "^1.0.4",
"hexo-generator-archive": "^1.0.0",
"hexo-generator-category": "^1.0.0",
"hexo-generator-copy": "^0.1.0",
"hexo-generator-index": "^2.0.0",
"hexo-generator-json-content": "^4.2.3",
"hexo-generator-search": "^2.4.2",
"hexo-generator-sitemap": "^2.1.0",
"hexo-generator-tag": "^1.0.0",
"hexo-hide-posts": "^0.1.1",
"hexo-pwa": "^0.1.3",
"hexo-renderer-ejs": "^1.0.0",
"hexo-renderer-marked": "^4.0.0",
"hexo-renderer-stylus": "^2.0.1",
"hexo-server": "^2.0.0",
"object-assign": "^4.1.1"
},
"devDependencies": {
"hexo-cli": "^4.2.0",
"hexo-feed": "^1.1.0",
"hexo-front-matter": "^2.0.0",
"hexo-fs": "^3.1.0"
}
}
```