Fix types for .cjs build (#16)

* Fix types for .cjs build

[Are the Types Wrong](https://arethetypeswrong.github.io/?p=memize%402.1.0) is currently reporting errors for memize:

> Problems
>
> * ❌ No types: Import resolved to JavaScript files, but no type declarations were found.
>
>
> ||"memize"
> |---|---|
> |node10	|✅|
> |node16 (from CJS)	|❌ No types|
> |node16 (from ESM)	|✅ (ESM)|
> |bundler	|✅|

For more information, see Are the Types Wrong's [UntypedResolution.md](https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/UntypedResolution.md). Note that the solution is not to point both the CJS and ESM builds at the same `.d.ts` file, for reasons explained in Are the Types Wrong's [FalseESM.md](https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseESM.md). Quoting that page:

> A golden rule of declaration files is that if they represent a module—that is, if they use import or export at the top level—they must represent exactly one JavaScript file. They _especially_ cannot represent JavaScript files of two different module formats.

The easiest solution I found was to run `tsc` a second time to build a `.d.cts` file.  For this second invocation, I pointed it at the Rollup-generated `.cjs` file.  (This is because tsc and Rollup by default handle default exports differently for CJS files: tsc translates `export default foo` to a `default` attribute on an object with `__esModule: true` and requires that you instead use `export =` for a "true" CommonJS export, while Rollup [by default](https://rollupjs.org/configuration-options/#output-exports) creates a "true" default export. By pointing tsc at the Rollup-generated `.cjs` file, tsc sees Rollup's `export =`.)

* Remove no longer needed `types`

Co-authored-by: Andrew Duthie <[email protected]>

* Remove more redundant `types` entries

Since we follow the default extensions, we shouldn't need to specify `types`.

---------

Co-authored-by: Andrew Duthie <[email protected]>

Author: joshkel

package.json

@@ -8,11 +8,10 @@
 		"import": "./dist/index.js",
 		"require": "./dist/index.cjs"
 	},
-	"types": "dist/index.d.ts",
 	"scripts": {
 		"build": "npm run build:bundle && npm run build:types",
 		"build:bundle": "rollup -c rollup.config.js",
-		"build:types": "tsc -b tsconfig.decl.json",
+		"build:types": "tsc -b tsconfig.decl.json && tsc -b tsconfig.decl.cts.json",
 		"test:unit": "NODE_ENV=test mocha",
 		"test:lint": "eslint .",
 		"test:types": "tsc -b",

tsconfig.decl.cts.json

@@ -0,0 +1,12 @@
+{
+	"extends": "./tsconfig.json",
+	"compilerOptions": {
+		"outDir": "dist",
+		"noEmit": false,
+		"declaration": true,
+		"emitDeclarationOnly": true
+	},
+	"files": [
+		"dist/index.cjs"
+	]
+}