feat: update BEM naming

lib/helpers/_block.scss

@@ -0,0 +1,70 @@
+/*
+ * Author: Sivan [sun.sivan@gmail.com]
+ * Description: define block helper classes.
+ */
+@import "../variables";
+
+@mixin hetiBlockHelperClasses {
+  /* 段落相关 */
+  // 元信息无缩进
+  #{$root-selector}-meta {
+    display: block;
+    text-indent: 0;
+  }
+
+  // 诗节无缩进，居中显示
+  #{$root-selector}-verse {
+    text-align: center;
+    text-indent: 0;
+  }
+
+  // 定义扩展字号
+  #{$root-selector} {
+    &-large {
+      font-size: $font-size-large;
+      line-height: $line-height-size-large;
+    }
+
+    &-x-large {
+      font-size: $font-size-x-large;
+      line-height: $line-height-size-x-large;
+    }
+
+    &-small {
+      font-size: $font-size-small;
+      line-height: $line-height-size-small;
+    }
+
+    &-x-small {
+      font-size: $font-size-x-small;
+      line-height: $line-height-size-x-small;
+    }
+  }
+
+  /* 列表相关 */
+  // 定义拉丁字母的有序列表
+  #{$root-selector}-list-latin {
+    list-style-type: upper-latin;
+
+    ol {
+      list-style-type: lower-roman;
+
+      ol {
+        list-style-type: lower-latin;
+      }
+    }
+  }
+
+  // 定义中文序号的有序列表
+  #{$root-selector}-list-han {
+    list-style-type: cjk-ideographic;
+
+    ol {
+      list-style-type: decimal;
+
+      ol {
+        list-style-type: decimal-leading-zero;
+      }
+    }
+  }
+}