chore: update documentation for block and custom directive usage

Clarifies the behavior of block overriding and inheritance in both English and Chinese documentation. Updates the CustomNode example to extend Traversal instead of implementing ASTNode, and improves explanations for include and block directives.

Author: vvenv

documentation-zh-CN.md

@@ -2,7 +2,7 @@
 
 ## 内置指令
 
-### **include**：模板继承/包含
+### **include**：模板继承与包含
 
 ```janja
 {{ include "template" }}
@@ -32,7 +32,9 @@
 {{ set foo }}内容{{ endset }}
 ```
 
-### **block / super**：模板继承与区块
+### **block / super**：区块覆盖与继承
+
+同名区块自动覆盖或继承，区块总是渲染在第一次出现的地方
 
 ```janja
 {{ block title }}{{ super }}默认标题{{ endblock }}
@@ -88,13 +90,15 @@ abs, capitalize, add, ceil, compact, div, entries, even, fallback, first, get, g
 ### 自定义指令
 
 ```typescript
-class CustomNode implements ASTNode {
+class CustomNode extends Traversal {
   readonly type = 'CUSTOM'
   constructor(
-    public val: string,
-    public loc: Loc,
-    public strip: Strip,
-  ) { }
+    public readonly val: string,
+    public readonly loc: Loc,
+    public readonly strip: Strip,
+  ) {
+    super()
+  }
 }
 render('{{ custom }}', {}, {
   parsers: {

documentation.md

@@ -2,6 +2,8 @@
 
 ## Built-in Directives
 
+### **include**: Template Inheritance & Inclusion
+
 ```janja
 {{ include "template" }}
 ```
@@ -30,7 +32,9 @@
 {{ set foo }}Content{{ endset }}
 ```
 
-### **block / super**: Template Inheritance & Blocks
+### **block / super**: Block Overriding & Inheritance
+
+Blocks with the same name will automatically overwrite or inherit, and blocks are always rendered where they first appear.
 
 ```janja
 {{ block title }}{{ super }}Default Title{{ endblock }}
@@ -86,13 +90,15 @@ abs, capitalize, add, ceil, compact, div, entries, even, fallback, first, get, g
 ### Custom Directive
 
 ```typescript
-class CustomNode implements ASTNode {
+class CustomNode extends Traversal {
   readonly type = 'CUSTOM'
   constructor(
-    public val: string,
-    public loc: Loc,
-    public strip: Strip,
-  ) { }
+    public readonly val: string,
+    public readonly loc: Loc,
+    public readonly strip: Strip,
+  ) {
+    super()
+  }
 }
 render('{{ custom }}', {}, {
   parsers: {