LibWeb: Add support for the “suggestion” ARIA role

[sideshowbarker]

[!NOTE] This PR currently includes a cherry-pick of the d0938d32ad1 commit from https://github.com/LadybirdBrowser/ladybird/pull/2843 — just for convenience so that we can have all PASSES for the expectations for all subtests in the relevant imported WPT test.

…but the d5c210b62fb commit here that adds support for the suggestion ARIA role can be reviewed separately here without needing to (re)review here that other commit from https://github.com/LadybirdBrowser/ladybird/pull/2843.

After https://github.com/LadybirdBrowser/ladybird/pull/2843 is merged, I can just rebase this PR branch.

Anyway, after the d5c210b62fb change here, and the d0938d32ad1 change from #2843, we’ll be passing 100% of the subtests in the roles.html test at https://wpt.fyi/results/wai-aria/role?product=ladybird.