feat: add gallery app for viewing/testing

gallery/run-debug.sh

@@ -0,0 +1,18 @@
+#!/bin/bash -e
+
+BUILD_DIR=build
+
+#NOTE: the PROJECT_VERSION is a dummy placeholder just for local builds
+if [ ! -d "$BUILD_DIR" ]; then
+  cmake -B$BUILD_DIR -S. -GNinja \
+    -DCMAKE_BUILD_TYPE=Debug \
+    -DCMAKE_CXX_FLAGS="-Wall -Wextra" \
+    -DCMAKE_PREFIX_PATH="$HOME/Qt/6.8.3/macos" \
+    -DCMAKE_COLOR_DIAGNOSTICS=ON \
+    -DCMAKE_CXX_FLAGS_INIT="-DQT_QML_DEBUG" \
+    -DCMAKE_OSX_ARCHITECTURES="arm64"
+fi
+
+cmake --build $BUILD_DIR --target all
+
+$BUILD_DIR/Gallery.app/Contents/MacOS/Gallery