1.0.6 — localized interface, clearer MyMemory message

- The interface is now available in English, German, French, Russian and
Japanese. It follows Thunderbird's own language; any other language shows
English. The language names in the settings appear in your language as well.
- Clearer message when MyMemory receives the same language twice. MyMemory
refuses a request whose source and target languages are identical, and its own
reply says nothing about which setting to change. The add-on now checks the
pair before sending anything, and names the setting: "Email language" is the
language your emails are written in, and it cannot be the same as the target
language. Google Translate and DeepL are unaffected — they detect the source
language themselves.
- The English wording was revised throughout, including the optional MyMemory
e-mail field, which now states plainly that it is neither a login nor a
registration.
- The bundled DOMPurify library was updated to 3.4.17.