Fix docs workflow, add WinUIBackend & GtkBackend to Windows workflow

Updated the Linux and macOS workflows to build the recently added
examples too.

Author: stackotter

.github/workflows/swift-linux.yml

@@ -31,6 +31,9 @@ jobs:
         swift build --target GreetingGeneratorExample && \
         swift build --target NavigationExample && \
         swift build --target SplitExample && \
+        swift build --target StressTestExample && \
+        swift build --target SpreadsheetExample && \
+        swift build --target NotesExample && \
         swift build --target GtkExample
     # - name: Test
     #   run: swift test

.github/workflows/swift-macos.yml

@@ -30,6 +30,9 @@ jobs:
         swift build --target GreetingGeneratorExample && \
         swift build --target NavigationExample && \
         swift build --target SplitExample && \
+        swift build --target StressTestExample && \
+        swift build --target SpreadsheetExample && \
+        swift build --target NotesExample && \
         swift build --target GtkExample
     # Calling `swift test` results in all targets getting built including targets such as WinUIBackend which
     # aren't available on macOS.

.github/workflows/swift-windows.yml

@@ -41,8 +41,12 @@ jobs:
       with:
         path: vcpkg_installed
         key: vcpkg-${{ steps.triplet.outputs.lowercase }}-${{ hashFiles('vcpkg.json') }}
-    - name: Build
+    - name: Build SwiftCrossUI
       env:
         PKG_CONFIG_PATH: ${{ github.workspace }}/vcpkg_installed/${{ steps.triplet.outputs.lowercase }}/lib/pkgconfig
       # Only build the library target to work around apple/swift-package-manager#6644
       run: swift build --target SwiftCrossUI -v
+    - name: Build WinUIBackend
+      run: swift build --target WinUIBackend
+    - name: Build GtkBackend
+      run: swift build --target GtkBackend

.github/workflows/update-docs.yml

@@ -6,12 +6,10 @@ on:
 
 jobs:
   update-docs:
-
     runs-on: ubuntu-latest
 
     steps:
     - uses: actions/checkout@v3
-    - uses: swift-actions/setup-swift@v1
     - name: Install Dependencies
       run: |
         sudo apt update && \