Use issue templates

[eganonoa]

This is a cleaned-up PR with issue templates (see #1069). The reasoning behind #1069 was as follows:

In its current form, Heads has so many variables it appears very difficult to determine the cause of issues being raised. There is a risk in development being stalled or taken off track by a rise of very specific bugs reported that are not readily reproducible or only appears in a very specific set of circumstances. In addition, its increasingly difficult to identify separate feature requests from bug reports.

These three templates provide templates for: (a) feature requests; (b) bug reports related to build errors for Heads; and (c) bug reports that come from the flashing or operation of Heads. They are designed to better help the identification of the best people to respond to any given issue, as well as to help triage issues.