Add functionality to recognize German verb forms

manuelaugustin commented 5 years ago

Summary

This PR can be summarized in the following changelog entry:

This PR includes basic verb functionality. This includes adding regular suffixes and generating forms for strong verbs. Extra functionality will be added in later PRs.

This PR can be tested by following these steps:

Make sure you have the premium configuration set to the right branch (see https://github.com/Yoast/YoastSEO.js-premium-configuration/pull/10).
Change the language of your site to German.
Add a German text and a keyphrase including German verbs.
Add different grammatical forms of the verbs in your text; make sure these forms are recognized. For this, you use forms of a specific word from a dictionary, e.g. https://de.wiktionary.org/wiki/Flexion:kaufen

Fixes #2132

manuelaugustin commented 5 years ago

Thanks for the tips! Now the code is quite a bit nicer/more efficient! 🙌

nataliashitova commented 5 years ago

Acceptance 👍 I've added a bunch of cases that do not work so far to https://github.com/Yoast/YoastSEO.js/issues/2160