Allow extract or set translation key with empty string

[cnwangjie]

Is your feature related to a specific framework or general for this extension

General

Is your feature request related to a problem? Please describe.

In my project, the copywriting is set by a dedicated team. Therefore, I only need to provide an i18n key. So I am developing through the TFunction call method. However, I cannot extract the key to a JSON file to provide it for translation to other teams.

Describe the solution you'd like

Now i18n-ally supports setting text for non-existent keys. You just need to allow empty strings to be set.

Additional context

As the image, I can set a text for a non-existent key. But I cannot set an empty string. We need an empty string to extract the text is enough.