Inserts a zero-width space in the `-->` which isn't supposed to close a
comment. This used to be here but it got lost in
d86826277d764217311d0d34a8e6143d09237a94.
PR #2413 added an issue template, but just adding files to the project
directory upsets the packaging scripts: we need to explicitly include or
exclude them.
Move the template into a .github directory to make that easy, and to de-clutter
the root a bit.
