[issue-template] Add 'General Issue' template
[issue-template] Add 'General Issue' template

The option to create a blank issue is hidden away which makes it
look like you have to create a chip-level test issue. Add a General
Issue template so that it is clear that you can create a blank issue
if there are no appropriate templates.

Signed-off-by: Michael Munday <19411bdeea90f848b8e02e9a1c63a7ce7cc699ea@lowrisc.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan