feat(issues): new format for issue templates (#2917)

* feat(issues): Added new, single issue template to capture issues in a more-easily triagable way

* feat(issues): Removed old issue templates to allow for new one to be non-optional

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,38 @@
+---
+name: New Issue
+labels: needs-triage
+---
+
+**Note: for support questions, please first reference our [documentation](https://docs.aws.amazon.com/cdk/api/latest), then use [Stackoverflow](https://stackoverflow.com/questions/ask?tags=aws-cdk)**. This repository's issues are intended for feature requests and bug reports.
+
+* **I'm submitting a ...**
+ - [ ] :beetle: bug report
+ - [ ] :rocket: feature request
+ - [ ] :books: construct library gap
+ - [ ] :phone: security issue or vulnerability => Please see [policy](https://github.com/awslabs/aws-cdk/security/policy)
+ - [ ] :question: support request => Please see note at the top of this template.
+
+
+* **What is the current behavior?**
+*If the current behavior is a :beetle:bug:beetle:: Please provide the steps to reproduce*
+
+
+
+* **What is the expected behavior (or behavior of feature suggested)?**
+
+
+
+* **What is the motivation / use case for changing the behavior or adding this feature?**
+
+
+
+* **Please tell us about your environment:**
+
+ - CDK CLI Version: xx.xx.xx
+ - Module Version: xx.xx.xx
+ - OS: [all | Windows 10 | OSX Mojave | Ubuntu | etc... ]
+ - Language: [all | TypeScript | Java | Python ]
+
+
+* **Other information** (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. associated pull-request, stackoverflow, gitter, etc)
+