Package Playground Composition (#12902)

## Description

This PR updates Playground Composition to have a packaging project and make it deployable. It also removes the now unnecessary elements in the playground composition project itself to better align it with the app template and move broadly shared things like the Windows SDK requirements into the shared files where it belongs.

Otherwise the PR avoids making any other major changes to Playground Composition code.

### Type of Change
- New feature (non-breaking change which adds functionality)

### Why
So that the base project setup that playground has doesn't drift from how the other new arch apps are set up.

Resolves #12758

### What
See above.

## Screenshots
N/A

## Testing
N/A

## Changelog
Should this change be included in the release notes: no

Author: jonthysell

change/react-native-windows-2bd0d917-fc69-41b9-bf3f-ba32bb117fc6.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Package Playground Composition",
+  "packageName": "react-native-windows",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}

packages/playground/README_composition.md

@@ -18,7 +18,7 @@ Playground is a sample standalone application that allows testing of various JS
 
 1. Open the app solution file in Visual Studio `packages\playground\windows\playground-composition.sln`
 
-1. Ensure **Playground-composition** project is set as startup project
+1. Ensure **playground-composition.Package** project is set as startup project
 
 1. Hit F5
 

packages/playground/windows/.gitignore

@@ -0,0 +1,41 @@
+*AppPackages*
+*BundleArtifacts*
+
+#OS junk files
+[Tt]humbs.db
+*.DS_Store
+
+#Visual Studio files
+*.[Oo]bj
+*.user
+*.aps
+*.pch
+*.vspscc
+*.vssscc
+*_i.c
+*_p.c
+*.ncb
+*.suo
+*.tlb
+*.tlh
+*.bak
+*.[Cc]ache
+*.ilk
+*.log
+*.lib
+*.sbr
+*.sdf
+*.opensdf
+*.opendb
+*.unsuccessfulbuild
+ipch/
+[Oo]bj/
+[Bb]in
+[Dd]ebug*/
+[Rr]elease*/
+Ankh.NoLoad
+.vs/
+# Visual C++ cache files
+
+#Files generated by the VS build
+**/Generated Files/**