(Copy) Pasting is broken! Handle clipboard better!

Issues: (Pasting into the Answer Editor)

• In Firefox, text is simply not pasted.
• In Chrome, text is pasted, but the cursor moves 2 characters behind the start of the pasted text. Unexpected behaviour!

Problem is here: components/Editor/index.tsx:L283.

It tries to intercept the default behaviour when files are found in the clipboard (to paste images). Yet somehow, even though preventDefault is never called, we cause some issues with what is supposed to happen. Further investigation required.

See !280 (merged) and !302 (merged) for changes that broke it. Do not rush merge requests...