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/value.ts

@@ -20,6 +20,7 @@ export class Value {
     this.initial = token.initial
     this.filters = token.filters.map(token => new Filter(token, this.getFilter(liquid, token.name), liquid))
   }
+
   public * value (ctx: Context, lenient?: boolean): Generator<unknown, unknown, unknown> {
     lenient = lenient || (ctx.opts.lenientIf && this.filters.length > 0 && this.filters[0].name === 'default')
     let val = yield this.initial.evaluate(ctx, lenient)
@@ -29,6 +30,7 @@ export class Value {
     }
     return val
   }
+
   private getFilter (liquid: Liquid, name: string) {
     const impl = liquid.filters[name]
     assert(impl || !liquid.options.strictFilters, () => `undefined filter: ${name}`)