Generate POT file

This could be a Composer script.

```shell
wp i18n make-pot src/ languages/plugin.pot --slug='plugin-slug' --package-name='Plugin Name' --headers='{"Report-Msgid-Bugs-To": "https://conedevelopment.com/hu/adatvedelem/", "Language-Team": "Cone Development <hello@conedevelopment.com>"}'
```
