* Throw Error for next.config.ts
Ref: https://github.com/zeit/next-plugins/issues/555
* Check for .js else .ts
* Update Error Message
Co-Authored-By: Alexander Kachkaev <alexander@kachkaev.ru>
* Add test case when both next.config.js and next.config.ts exist.
* Remove extra constant CONFIG_FILE_TS and Add check for ts/tsx/json
* Rename test config parameter and add tsx and json files
* Change messege
* change value
* Update next.config.json
* Update next.config.json
* Change message and add jsx filter
* Adjust
* Simplify test
* adjust
