perf: introduce AST to avoid reparse

test/integration/liquid/root.ts

@@ -0,0 +1,15 @@
+import { normalize } from '../../../src/liquid-options'
+import { expect } from 'chai'
+
+describe('LiquidOptions#root', function () {
+  describe('#normalize ()', function () {
+    it('should normalize string typed root array', function () {
+      const options = normalize({ root: 'foo' })
+      expect(options.root).to.eql(['foo'])
+    })
+    it('should normalize null typed root as empty array', function () {
+      const options = normalize({ root: null } as any)
+      expect(options.root).to.eql([])
+    })
+  })
+})