Language switcher block flags styling improvement

Problem/Motivation

When flags_language is enabled and the core Language switcher block (language_block:language_interface) is placed on a page, the rendered block shows default unordered-list bullets and the flag icon sits above the language label baseline.

Steps to Reproduce

1. Install flags and enable flags_language.
2. Enable two or more languages.
3. Place the Language switcher (Interface text language detection) block in any region of the default theme (e.g. Olivero highlighted).
4. View any page that renders the block.

Observed: visible bullets, flag floats above the text baseline.

Proposed Resolution

Ship a small, language-switcher-scoped stylesheet in flags_language so the sprite CSS in flags/flags stays a generic utility and the switcher styling lives where it belongs.

Remaining Tasks

Review