Support passing command line flags to start the browser.

[brendandahl]

e.g. --browser-arg="--enable-unsafe-webgpu" --browser-arg="--js-flags=\"--experimental-wasm-fp16\""

[brendandahl]

FWIW, I wanted to make it so you can put them all in one flag, but there's some weirdness happening with how webdriver args works and using the --js-flags. I could probably fix it, but then we'd need to parse the arguments, which seems like overkill.

[rmahdav]

Question: These browser args are passed when the tests in CI are running? Or they also can be passed if someone trying to run the benchmark locally? I am trying to figure out if we need to edit README file as well or not.

[brendandahl]

They currently just work with running the test scripts directly. This is what I'm using to run on my cloudtop: node tests/run-end2end.mjs --browser chrome --browser-arg="--enable-unsafe-webgpu".

[rmahdav]

Got it, thanks!