include directx 5 sdk

This is almost certainly abandonware, fairly small (<1MB), and is going to save us a lot of dev environment headaches

.github/workflows/build.yml

@@ -14,34 +14,6 @@ jobs:
         repository: 'itsmattkc/msvc420'
         path: msvc420
 
-    - name: Restore cached DX5 SDK
-      id: cache-dx5
-      uses: actions/cache/restore@v3
-      with:
-        path: dx5sdk
-        key: dx5sdk
-
-    - name: Download DX5 SDK
-      if: ${{ !steps.cache-dx5.outputs.cache-hit }}
-      run: |
-        cd dx5sdk
-        curl -fLOSs https://archive.org/download/idx5sdk/idx5sdk.exe
-        7z x .\idx5sdk.exe
-        7z x .\DX5SDK.EXE
-
-    - name: Cache DX5 SDK
-      if: ${{ !steps.cache-dx5.outputs.cache-hit }}
-      uses: actions/cache/save@v3
-      with:
-        path: dx5sdk
-        key: dx5sdk
-
-    - name: Setup DX5 SDK
-      run: |
-        cd dx5sdk
-        cd cdrom
-        .\SETUP.EXE /s
-
     - name: Setup cmake
       uses: jwlawson/actions-setup-cmake@v1.13
       with: