Create a JSON library for tools

As the number of tools is increasing in order to manage to show the tool in a more dynamic way, I would suggest creating a JSON file and store the tool's information inside the JSON objects.

One key advantage of such implementation is that in the future we can show all tools on the first page by looping through the JSON array of tools. Then the contributors just need to update the JSON file and their tool will be shown on the first page automatically.

Suggested Format:

```json
{
"conversionTools": [
{
"title": "Angle Conversion",
"description": "bla bla",
"url": "/Angle_Conversion/angleconversions.html"
}
],
}
```

No files or tests are named. Start by locating how the current tools are listed and how the first page renders them, then define the JSON data shape and connect the existing display to it; done means tools can be represented in the JSON and shown dynamically.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.