Allow different campaigns for download button

[hoosteeno]

Description

The download button we use in most places on our website currently has hard-coded UTM parameters for referrals to app stores. We should enable a specific template to pass in different utm_campaign and utm_content params that will be added to the URLs for mobile Firefox installs on app stores.

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:yellow_heart: Success Criteria :yellow_heart:

• [ ] A template can pass utm_campaign and utm_content params into the series of helpers that create download buttons, such that mobile download button links include those parameters.

┆Issue is synchronized with this Jira Task ┆Priority: (none) ┆Sprint: Backlog