Generate Spec tests from Shopify/liquid-wasm

Liquid-WASM has its own list of spec tests, and Liquid-Spec should be able to import spec tests from it: ([Wasm PR](https://github.com/Shopify/liquid-wasm/pull/492/files))
```bash
rake generate
rake generate:liquid_ruby # Generate spec tests from Shopify/liquid
rake generate:liquid_wasm # Generate spec tests from Shopify/liquid-wasm
```