* feat: support artalk comment system * chore: change url from testingcf to cdn prefix * refactor(comments): align artalk provider style and keep custom css overrides * fix: update Artalk CDN links to use the correct URL * refactor(comments): simplify Artalk implementation * fix(artalk): update script tag to use ESM for Artalk * fix(artalk): set locale to 'auto' for Artalk comments * refactor: move artalk style and script link to external.toml --------- Co-authored-by: Jimmy Cai <jimmy@cai.im>