Search content component

```elixir
<%= BeaconWeb.Components.search_content %>
```

Parameters:
- Function to customize query
- Query input
- Block to display results with a default implementation

Useful for content like https://dockyard.com/blog

Start by locating the `BeaconWeb.Components.search_content` entry point shown in the issue; no file or test is named. Clarify how the query-customizing function, query input, and results block should work, including the default results display. Done means the component supports those parameters for searching content such as blog posts.

Written by the indexing model from the issue text.