perf: introduce AST to avoid reparse

src/tokens/number-token.ts

@@ -0,0 +1,12 @@
+import { Token } from './token'
+import { WordToken } from './word-token'
+import { TokenKind } from '../parser/token-kind'
+
+export class NumberToken extends Token {
+  constructor (
+    public whole: WordToken,
+    public decimal?: WordToken
+  ) {
+    super(TokenKind.Number, whole.input, whole.begin, decimal ? decimal.end : whole.end, whole.file)
+  }
+}