Adds support for data output for devcenter search

[gilzow]

Why

The devcenter search requires a specific data structure for its search, that differs considerably from the structure meilisearch requires. In the interest of time, we're going to add a secondary data output for each docs site for the devcenter to consume.

What's changed

• adds new output format for devcenter-specific search data to config for both sites
• adds new devcenter.json template to layouts
• adds supporting partials to generate the json layout

Where are changes

Updates are for: [X] platform (sites/platform templates) [X] upsun (sites/upsun templates)

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