refactor(lexer, ast): Rewrite decl with c standard grammar of decl

src/lexer/types.rs

@@ -25,7 +25,7 @@ pub enum TokenValue {
     LBracket, RBracket,
     Comma, Semicolon,
 
-    If, Else, While, For, Return, Break, Continue,
+    If, Else, While, For, Return, Break, Continue, Static,
 
     Eof,
     Unrecognized,
@@ -84,6 +84,7 @@ impl std::fmt::Display for TokenValue {
             TokenValue::Return => write!(f, "return"),
             TokenValue::Break => write!(f, "break"),
             TokenValue::Continue => write!(f, "continue"),
+            TokenValue::Static => write!(f, "static"),
             TokenValue::Eof => write!(f, "end of input"),
             TokenValue::Unrecognized => write!(f, "unrecognized"),
         }
@@ -104,7 +105,7 @@ pub enum TokenKind {
     LBracket, RBracket,
     Comma, Semicolon,
 
-    If, Else, While, For, Return, Break, Continue,
+    If, Else, While, For, Return, Break, Continue, Static,
 
     Eof,
     Unrecognized,