[Feat] 模块系统支持，使用 import x.x.x导入

[Fix] Context内部辅助函数修改, getStructName ....
[Feat] 增加字符串下标获取操作，和修改字符操作，实现使用了第四点的函数
[Impl] FString添加新方法 getRealChar, realReplace
[Fun] 在utf8_iterator中辱骂了C++

src/Ast/Statements/ImportSt.hpp

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <Ast/astBase.hpp>
+
+#include <vector>
+
+namespace Fig::Ast
+{
+    class ImportSt final : public StatementAst
+    {
+    public:
+        std::vector<FString> path;
+        
+        ImportSt()
+        {
+            type = AstType::ImportSt;
+        }
+
+        ImportSt(std::vector<FString> _path) :
+            path(std::move(_path)) 
+        {
+            type = AstType::ImportSt;
+        }
+    };
+
+    using Import = std::shared_ptr<ImportSt>;
+};

src/Ast/ast.hpp

@@ -20,6 +20,7 @@
 #include <Ast/Statements/StructDefSt.hpp>
 #include <Ast/Statements/IfSt.hpp>
 #include <Ast/Statements/ImplementSt.hpp>
+#include <Ast/Statements/ImportSt.hpp>
 #include <Ast/Statements/FunctionDefSt.hpp>
 #include <Ast/Statements/ControlSt.hpp>
 #include <Ast/Statements/ExpressionStmt.hpp>

src/Ast/astBase.hpp

@@ -50,12 +50,15 @@ namespace Fig::Ast
         ElseSt,
         ElseIfSt,
 
-        VarAssignSt,
+        // VarAssignSt,
         WhileSt,
         ForSt,
         ReturnSt,
         BreakSt,
         ContinueSt,
+
+        PackageSt,
+        ImportSt,
     };
 
     // static const std::unordered_map<AstType, FString> astTypeToString{