Fix `<!DOCTYPE html>` syntax highlighting (#9108)

Max created

Release Notes:

- Added `<!DOCTYPE html>` syntax highlighting ([4318](https://github.com/zed-industries/zed/issues/4318))

Change summary

crates/languages/src/html/highlights.scm | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

Detailed changes