chore: further restrict usernames

closes #186

crates/delta/src/util/regex.rs

@@ -6,4 +6,4 @@ use regex::Regex;
 /// Block zero width space
 /// Block lookalike characters
 pub static RE_USERNAME: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^[^\u200BА-Яа-яΑ-Ωα-ω@#:\n]+$").unwrap());
+    Lazy::new(|| Regex::new(r"^[^\u200BА-Яа-яΑ-Ωα-ω@#:\n\r\[\]]+$").unwrap());