feat(gx): add incomplete 'CGxDeviceGLSDL' (#2)

* chore(build): add vendored SDL 3.0.0 library

* chore(build): add vendored glew-cmake-2.2.0 library

* feat(console): in the presence of -opengl launch flag, change GxApi to OpenGl

* feat(gx): add uncompleted CGxDeviceGLSDL targeting Windows and Linux

* chore(build): change SDL3 linkage from shared (bad) to to static (good)

vendor/sdl-3.0.0/.github/workflows/visionos.yml.disabled

@@ -0,0 +1,22 @@
+name: Build (visionOS)
+
+# FIXME: Enable this workflow once CMake 3.28 becomes available on GitHub
+on: [push, pull_request]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  Build:
+    name: visionOS
+    runs-on: macos-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Configure
+        run: |
+          cmake -B build -GXcode -DCMAKE_SYSTEM_NAME=visionOS
+      - name: Build
+        run: |
+          cmake --build build