Add support for Umami analytics

[mikecao]

Hi, I'm the founder of Umami Analytics. I saw that you had an analytics integration section, https://mintlify.com/docs/integrations/analytics/overview, and would love to get included.

The implementation would look like this:

"analytics": {
  "umami": {
    "websiteId": "required",
    "hostUrl": "optional"
  }
}

The parameters would generate the following script:

<script defer src="{hostUrl}" data-website-id="{websiteId}"></script>

if hostUrl is not specified, it should default to https://cloud.umami.is/script.js.

Great product btw! We were looking for a solution for our own docs and found Mintlify.