add parser / grammar and spec

docs/contribute/parser.md

@@ -4,3 +4,27 @@ title: Parser
 ---
 
 # Parser
+
+# Conformance Tests
+
+This details the three GitHub repositories for testing our parser against JavaScript and TypeScript grammar.
+
+## Test262
+
+JavaScript has the [ECMAScript Test Suite](https://github.com/tc39/test262) called Test262.
+The goal of Test262 is to provide test material that covers every observable behavior specified in the specification.
+
+For testing conformance, please checkout its [parse phase tests](https://github.com/tc39/test262/blob/main/INTERPRETING.md#negative).
+
+## Babel
+
+When new language features are added to JavaScript, it is required to have them get parsed by Babel.
+So Babel has another set of [parser tests](https://github.com/babel/babel/tree/main/packages/babel-parser/test).
+
+## TypeScript
+
+The TypeScript conformance tests can be found [here](https://github.com/microsoft/TypeScript/tree/main/tests/cases/conformance).
+
+## Test Runner
+
+Rome has implemented a test runner for the above test suites, they can be found [here](https://github.com/rome/tools/tree/main/xtask/coverage).