Add link to privacy policy to footer (for GDPR compliance)

[holgerd]

In the lower right corner of https://wheelmap.org/ is a text link "Impressum" / "Imprint". This leads to https://news.wheelmap.org/impressum/ if the language is German and to https://news.wheelmap.org/en/imprint/ in any other language.

To the right side of this text link we need another textlink following the same logic.

Text:

• "Datenschutzbedingungen" in German and
• "Privacy Policy" in any other language (please discuss translation implications with @Svenyo )

Link:

• in German: https://news.wheelmap.org/datenschutz/
• in any other language: https://news.wheelmap.org/en/privacy/