Generate search index for Sample App

We should generate an index of all the common terms across all markdown documents and sample code.

This index should be part of the sample app so we can provide quick and comprehensive searching within our documentation and samples within the app without having to load all the documentation contents and sample contents first.

This should be done with a source generator at compile time (and probably have a 'light-mode' for debug vs. a comprehensive index for release mode)?

Start by locating the sample app and the markdown and sample-code inputs it includes. Review how source generators are configured, then determine how a debug light-mode and comprehensive release index should be produced and consumed. Done means the app can search documentation and samples without loading their full contents first.

Vom Indexierungsmodell aus dem Issue-Text verfasst.