chore(TypeScript): refactor objects into classes

fix: `Nil`(null, undefined) now renders as empty string
change: `parser.parseValue()` renamed to `parser.parseOutput`
change: registered tags/filters become static and shared across different liquid instances

src/parser/token.ts

@@ -0,0 +1,14 @@
+export default class Token {
+  type: string
+  line: number
+  raw: string
+  input: string
+  file: string
+  value: string
+  constructor(raw, pos, input, file, line) {
+    this.line = line
+    this.raw = raw
+    this.input = input
+    this.file = file
+  }
+}