Use multiple GitHub issue templates for bugs, feature requests and support questions

[bergmeister]

PR Summary

Since the beginning of 2018, GitHub supports multiple issue/PR templates and since May the 2nd, there is also UI integration for it (see here)
To have more useful and specific templates:

• The bug template also has an additional command on how to dump the stack trace and asks the user to use the latest version and perform a quick search for existing issues
• The new feature template adds some hints on how to describe a new feature
• The support template link to the scriptanalyzer channel on Slack

I created an example of how this would look like in a test repo here

PR Checklist

Note: Tick the boxes below that apply to this pull request by putting an x between the square brackets. Please mark anything not applicable to this PR NA.

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• NA User facing documentation needed
• NA Change is not breaking
• NA Make sure you've added a new test if existing tests do not effectively test the code changed
• This PR is ready to merge and is not work in progress
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready