feat: static variable analysis (#770)

* feat: static variable analysis

* Accept any iterable from `children`, `arguments`, etc.

* Test analysis of standard tags

* Use `TagToken.tokenizer` instead of creating a new one

* Test analysis of netsted tags

* Group variables by their root value

* Test analysis of nested globals and locals

* Analyze included and rendered templates WIP

* Use existing tokenizer when constructing `Hash`

* Improve test coverage

* Analyze variables from `layout` and `block` tags

* Test analysis of Jekyll style includes

* Handle variables that start with a nested variable

* Async analysis

* Test non-standard tag end to end

* Implement convenience analysis methods on the `Liquid` class

* More analysis convenience methods

* Accept string or template array

* Draft static analysis docs

* Deduplicate variables names

* Fix isolated scope global variable map

* Coerce variables to strings instead of extending String

* Private map instead of extending Map

* Fix e2e test

* Tentatively implement analysis of aliased variables

* Fix nested variable segments array

* Update docs sidebar

src/template/hash.spec.ts

@@ -1,6 +1,7 @@
 import { toPromise } from '../util'
 import { Hash } from './hash'
 import { Context } from '../context'
+import { Tokenizer } from '../parser'
 
 describe('Hash', function () {
   it('should parse "reverse"', async function () {
@@ -43,4 +44,10 @@ describe('Hash', function () {
     const hash = await toPromise(new Hash('num=2.3', '=').render(new Context()))
     expect(hash.num).toBe(2.3)
   })
+  it('should accept an existing tokenizer', async function () {
+    const tokenizer = new Tokenizer('a:1, b:2')
+    const hash = await toPromise(new Hash(tokenizer).render(new Context()))
+    expect(hash.a).toBe(1)
+    expect(hash.b).toBe(2)
+  })
 })