add details/summary to issue template

[piksel]

This will make the log section of an issue expandable (and preformatted) by default.

Like this

This is really useful when reading large amounts of text from the console, like logs etc.
The problem is that it's neither-well known, nor easy to get right since you need to put a single 
blank line separating HTML and markdown parts.

Not sure if it's clear enough for people creating the issue how to correctly fill it in. A comment (<!-- -->) could be added to explain where to put the log rows, but it might also just be more confusing....

[zoispag]

I was totally thinking the same today. I am in favor of adding html comments as well, to instruct what and how.