allow for local run of project

Currently the only way to run this is using the npx version. This only works in systems where npx is installed.

It would be beneficial to allow building based on the pre-compiled version of Pagefind.

## How to do this

- It could be a setting that is passed as a plugin_extras

`{path: 'npm'} # this would allow for other options like "rust" and anything else could be the path.

Locate the current npx invocation and the handling of plugin_extras, then trace how Pagefind is built or launched. Support a configurable path for a pre-compiled Pagefind version and verify that the project can run locally without npx.

Written by the indexing model from the issue text.