hardcode deepl v1 tag handling

fix provided by user @annda on GitHub

Add option to use old tag handling

keep relative links when translating

Relative links should usually work fine as-is and would not need any
rewriting. Since there are no tests, I added a config to not change the
default behaviour.

add glossary feature

add option if the default language is a language namespace

add push translate feature

add error messages and re-render escaped html-chars

add translate menu button

initial commit