Typescript requires commonjs type definitions to have a .cts extension
when resolving from package.json exports. Add a demo that illustrates
the error.

 - csv-demo-browser@0.1.4
 - csv-demo-cjs@0.2.2
 - csv-demo-eslint@0.1.8
 - csv-demo-esm@0.0.16
 - csv-issues-cjs@0.1.3
 - csv-issues-esm@0.0.7
 - csv-demo-ts-moduleresolution-node16-cjs@0.2.2
 - csv-demo-ts-module-node16@0.2.2
 - csv-demo-webpack-ts@0.1.4
 - csv-demo-webpack@0.1.6
 - csv-generate@4.2.2
 - csv-parse@5.3.5
 - csv-stringify@6.2.4
 - csv@6.2.7
 - stream-transform@3.2.2