Added a separate advanced options settings panel with flags

- Added gpu-rasterization flag

config setting `disableHardwareMediaKeys` moved to `flags.disableHardwareMediaKeys`, it will be migrated automatically

src/constants/flags.js

@@ -0,0 +1,6 @@
+const flags = {
+  gpuRasterization: [{ flag: "enable-gpu-rasterization", value: undefined }],
+  disableHardwareMediaKeys: [{ flag: "disable-features", value: "HardwareMediaKeyHandling" }],
+};
+
+module.exports = flags;