GitHub issue templates

[achimmihca]

What does this PR do?

Minor adjustments to the GitHub issue templates, notably the bug report.

• I found that often a log file and details about the song file format are useful. This is why I explicitly added bullet points for these.
• The checkbox for "reproducible" implies that the user should try to reproduce the issue.
• The idea behind the section for "implementation hints" is to separate the actual issue and potential solutions. I found that sometimes people try to come up with a solution first, thereby skipping the formulation of the initial problem.