Remove formatting when content is pasted into tinymce editor

[timobrembeck]

Motivation

At the moment, formatting is preserved when texts are copied from e.g. word or websites into the tinymce text area.
Only Strg + Shift + V removes the formatting, but not all users know about this.

Proposed Solution

Also remove the formatting when Strg + V is used

Alternatives

Add the possibility to modify the font and size in the editor

Additional Context

If possible, preserve links in the content.

[osmers]

The alternative is not very preferable since it would destroy uniformity in the Integreat App