Add `search` skill for defining how to hook up app search

[michael-hawker]

This skill should do two things:

1. Talk about the design level of using things like AutoSuggestBox either alone or built-in to NavigationView or a Titlebar.

• Where to put them, why, not having them all over, etc... (usability)
• How to differentiate multiple boxes if needed (i.e. local settings page search vs. app-level search)

2. Implementing search as a pattern to display results efficiently

• async patterns (any learnings from CmdPal would be good here @niels9001)
• indexing
• display/MVVM
• AI: local RAG/indexing models, etc...

[marcelwgn]

100% agree on the first part, second part seems too open ended to give meaningful advice besides "do it off the UI thread". What if my app is using a DB in for state? what if its using an http API? Not sure if win-dev-skills is the right place to teach about search implementations and optimizations