feat: add raw-query option for search bangs

[NecRaul]

This PR introduces a new optional raw-query flag for search bangs, giving users control over whether {QUERY} is URL encoded before being inserted into the bang URL.

What this changes

• Adds raw-query: boolean to the bang configuration schema.
• Defaults to false to preserve the existing behavior.
• When raw-query: true, {QUERY} is substituted as-is, without encodeURIComponent.
• Updates:
  • Documentation (configuration.md)
  • HTML template (search.html)
  • Client-side behavior (page.js)
  • Bang struct (widget-search.go)

Why

This resolves issue #527, allowing certain shortcuts to receive an unencoded path-style query. This is especially useful for URLs where slashes or special characters are meaningful, such as GitHub paths.