fix: reenable json5 parser

continues #174

src/main/ts/util.ts

@@ -24,7 +24,14 @@ export const remove = fse.unlinkSync
 export const unixify = (path: string): string => path.replace(/\\/g, '/')
 
 export const resolveTsConfig = (file: string): TSConfig => populateSync(file, {
-  compilerOptions: 'merge'
+  parse({contents, ext}) {
+    if (ext === '.json')
+      return json5.parse(contents)
+    throw new Error(`Unsupported format: ${ext}`)
+  },
+  rules: {
+    compilerOptions: 'merge'
+  }
 })
 
 export const omitUndefinedKeys = <T extends Record<string, any>>(obj: T): T  =>

src/test/fixtures/ts-project/tsconfig.es6.json

@@ -5,5 +5,6 @@
     "module": "esnext",
     "outDir": "target/es6"
   },
+  // json5 comment
   "include": ["src/main/**/*.ts"]
 }