Use querySelector over alternative DOM methods (#31280)

As per
https://github.com/go-gitea/gitea/pull/30115#discussion_r1626060164,
prefer `querySelector` by enabling
[`unicorn/prefer-query-selector`](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/prefer-query-selector.md)
and autofixing all except 10 issues.

According to
[this](https://old.reddit.com/r/learnjavascript/comments/i0f5o8/performance_of_getelementbyid_vs_queryselector/),
querySelector may be faster as well, so it's a win-win.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

.eslintrc.yaml

@@ -798,7 +798,7 @@ rules:
   unicorn/prefer-object-has-own: [0]
   unicorn/prefer-optional-catch-binding: [2]
   unicorn/prefer-prototype-methods: [0]
-  unicorn/prefer-query-selector: [0]
+  unicorn/prefer-query-selector: [2]
   unicorn/prefer-reflect-apply: [0]
   unicorn/prefer-regexp-test: [2]
   unicorn/prefer-set-has: [0]