Add Notes App for AppContentSearch Samples

[karkarl]

Description

Add Notes sample app to showcase AppContentSearch capabilities in WindowsAppSDK 2.0 exp2

Target Release

WindowsAppSDK 2.0 exp2

Checklist

Note that /azp run currently isn't working for this repo.

• [ ] Samples build and run using the Visual Studio versions listed in the Windows development docs.
• [ ] Samples build and run on all supported platforms (x64, x86, ARM64) and configurations (Debug, Release).
• [ ] Samples set the minimum supported OS version to Windows 10 version 1809.
• [ ] Samples build clean with no warnings or errors.
• [x ] [For new samples]: Samples have completed the sample guidelines checklist and follow standardization/naming guidelines.
• [ x] Microsoft employees only: you can validate your changes by following the instructions here: https://www.osgwiki.com/wiki/WindowsAppSDK-Samples