wait until document loaded to scan pages

TL;DR
The scanner seems to be finding some violations that aren't accurate. This could be due to the page not being fully loaded yet (dynamically generated content).

Playwright allows us to wait until page content is loaded: https://playwright.dev/docs/api/class-page#page-goto-option-wait-until

See this thread for context: https://github.slack.com/archives/C0FSWLQ0Y/p1765992292609119