Website: Add download statistics page

[damienalexandre]

Just for fun we could add a download stats page on the website.

A bit like https://symfony.com/stats/downloads

Based on Github API we can extract the download for each type of releases.

$ gh api /repos/jolicode/castor/releases | jq ".[] | {name: .name, assets: [.assets[] | {name: .name, count: .download_count}]}"

This API gives for example, for each release:

{
  "name": "Release v0.18.2",
  "assets": [
    {
      "name": "castor.linux-arm64.phar",
      "count": 3
    },
    {
      "name": "castor.darwin-amd64",
      "count": 9
    },
    {
      "name": "castor.windows-amd64.phar",
      "count": 25
    },
    {
      "name": "castor.darwin-amd64.phar",
      "count": 33
    },
    {
      "name": "castor.darwin-arm64.phar",
      "count": 86
    },
    {
      "name": "castor.linux-amd64",
      "count": 3940
    },
    {
      "name": "castor.linux-amd64.phar",
      "count": 10928
    }
...