Developer responsibilities and tasks

Key responsibilities of developers listed, as well as some more specific tasks / responsibilities that are not common to all developers. Looking forward to input from our Developers and Service Engineers!

(btw, would be great to do a \cc @developers, but that's not possible right?)

\cc @sytses @dzaporozhets @marin @jacobvosmaer @JobV @vsizov @patricio @DouweM @ayufan @rspeicher @jnijhof @dblessing @yorickpeterse