Auto merge of rust-lang#6147 - dwijnand:issue-templates, r=JoshTriplett

Introduce issue templates

I took GitHub's default "Bug report" and "Feature request" templates and modified them a bit to make them work with Cargo.  Happy to iterate more.  WDYT?

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,27 @@
+---
+name: Bug report
+about: Create a report to help us improve
+---
+
+<!-- Thanks for filing a 🐛 bug report 😄! -->
+
+**Problem**
+<!-- A clear and concise description of what the bug is. -->
+<!-- including what currently happens and what you expected to happen. -->
+
+**Steps**
+<!-- The steps to reproduce the bug. -->
+1.
+2.
+3.
+
+**Possible Solution(s)**
+<!-- Not obligatory, but suggest a fix/reason for the bug, -->
+<!-- or ideas how to implement the addition or change -->
+
+**Notes**
+
+Output of `cargo version`:
+
+<!-- Also, any additional context or information you feel may be relevant to the issue. -->
+<!-- (e.g rust version, OS platform/distribution/version, target toolchain(s), release channel.. -->

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,15 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+---
+
+<!-- Thanks for filing a 🙋 feature request 😄! -->
+
+**Describe the problem you are trying to solve**
+<!-- A clear and concise description of the problem this feature request is trying to solve. -->
+
+**Describe the solution you'd like**
+<!-- A clear and concise description of what you want to happen. -->
+
+**Notes**
+<!-- Any additional context or information you feel may be relevant to the issue. -->