Revise issue template

[HebaruSan]

Monitoring the new issue queue, a few patterns are apparent. There are some questions we don't ask in the issue template that we should, as well as some questions that don't generally receive productive responses. And a lot of people don't delete the instructional text at the top.

This pull request modifies the issue template:

• Put the introductory text in a comment since it's not needed after the issue is submitted
• Added link to where you can do a search of open issues
• Split into background/problem sections
• Added space between questions to encourage more consistent formatting 🤞
• Added question about KSP version since many issues are version-specific
• Added question about manual modifications to GameData since this is a frequent cause of issues
• "Issue you are experiencing" and "How to recreate" replaced by steps taken, expected result, and actual outcome
• Added screenshots section with instructional comment in case the reader doesn't know how

[Olympic1]

Oh, didn't know that you could add comments to the template.