fix: 修改 email 的正则常量

1. fix: Email 的 Pattern 不区分大小写
2. docs: 标注正则表达式的出处

src/main/java/xyz/zhouxy/plusone/commons/constant/PatternConsts.java

@@ -61,7 +61,7 @@ public final class PatternConsts {
      *
      * @see RegexConsts#EMAIL
      */
-    public static final Pattern EMAIL = Pattern.compile(RegexConsts.EMAIL);
+    public static final Pattern EMAIL = Pattern.compile(RegexConsts.EMAIL, Pattern.CASE_INSENSITIVE);
 
     /**
      * 中国大陆手机号