Add 'src' to package.json files to improve source maps (jaredpalmer#620)

- so library users can actually view source, add breakpoints there,
  etc, etc and not only view types and dist files

Co-authored-by: Anton Gilgur <agilgur5@gmail.com>
Co-authored-by: Yordis Prieto <yordis.prieto@gmail.com>

src/templates/basic.ts

@@ -11,7 +11,7 @@ const basicTemplate: Template = {
     main: 'dist/index.js',
     // module: `dist/${safeName}.esm.js`,
     typings: `dist/index.d.ts`,
-    files: ['dist'],
+    files: ['dist', 'src'],
     engines: {
       node: '>=10',
     },