Update issue templates

Create `bug report` and `feature request` templates.

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: You found an unexpected behaviour? Use this template.
+
+---
+
+<!-- Think about the title, twice. -->
+
+<!-- Summarize the Problem here, keep it simple. -->
+<!-- e.g. `echo` outputs the wrong string. -->
+
+
+### Example
+<!-- This should be a source code block. 
+```nim
+echo "Hello World!"
+```
+-->
+
+
+### Current Output
+<!--
+```
+Hola mundo!
+```
+-->
+
+
+### Expected Output
+<!--
+```
+Hello World!
+```
+-->
+
+
+### Possible Solution
+<!--- Have you found a possible solution? Post it here. -->
+
+
+### Additional Information
+<!--- For Example:
+   A link to a project where the issue is relevant.
+   A link to a related issue or discussion.
+-->

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,23 @@
+---
+name: Feature request
+about: You want to suggest a new feature? Use this template.
+
+---
+
+### Summary
+<!--- Short summary of your proposed feature -->
+
+
+### Description
+<!--- Describe your solution, what problem does it fix? -->
+
+
+### Alternatives
+<!--- Are there any alternatives you've considered? -->
+
+
+### Additional Information
+<!--- For Example:
+   A link to a project where the issue is relevant.
+   A link to a related issue or discussion.
+   -->