Update pyproject.toml to add Playwright as a Dependency

[jumarmartin]

Problem

When we run setup.sh we fail to setup playwright through uv.

Why

Since playwright is not specified in the pyproject.toml, we never install it when running the second step in setup.sh:

webarena-infinity/setup.sh

Lines 11 to 17 in 1ca7781

	# 1. Python dependencies
	echo "Installing Python dependencies..."
	uv sync
	# 2. Playwright browser
	echo "Installing Playwright Chromium..."
	uv run python -m playwright install chromium

So, when we try to setup playwright, we can't.

Solution

Add playwright to the dependency array.