Update Umami Analytics support to include custom script URL option

[AlixANNERAUD]

Hi :wave:, Thanks for this awesome work on this theme.

This pull request adds support for specifying a custom script URL for Umami Analytics, allowing users to override the default region-based script. The documentation and analytics partial have been updated to reflect this new option.

This is related to : https://github.com/jpanther/congo/discussions/829#discussioncomment-11773875

Changes

Umami Analytics configuration improvements:

• Added umamiAnalytics.script parameter to the configuration documentation (exampleSite/content/docs/configuration/index.md) to allow specifying a custom script URL for Umami Analytics.
• Updated the Umami Analytics documentation to explain how to use the new script parameter for custom or proxied script URLs, and clarified its precedence over the region parameter (exampleSite/content/docs/partials/index.md).

Template logic update:

• Modified the analytics partial (layouts/_partials/analytics.html) to use the custom script URL if provided, falling back to the region-based default if not.

Testing

This has been tested locally with the following settings.

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[AlixANNERAUD]

Updates ?