Add issue templates on GitHub (#501)

.github/ISSUE_TEMPLATE/--bug-report.md

@@ -0,0 +1,24 @@
+---
+name: "\U0001F41BBug report"
+about: Create a bug report about GDevelop or the game engine
+
+---
+
+## Describe the bug
+A clear and concise description of what the bug is.
+
+Please double check that the bug is not already reported in the issues list.
+
+## To Reproduce
+Steps to reproduce the behavior:
+1. Go to '...'
+2. Click on '....'
+3. Scroll down to '....'
+4. See error
+
+* Please include a link to a game if possible!
+* If applicable, add screenshots to help explain your problem.
+
+## Other details
+* Include any OS/browser version/smartphone that you're using
+* Add any other context about the problem here.

.github/ISSUE_TEMPLATE/--feature-request.md

@@ -0,0 +1,26 @@
+---
+name: "\U0001F4A1Feature request"
+about: Suggest an idea for this project AFTER discussing about it on the Discord or
+  Forum first.
+
+---
+
+BEFORE opening a new feature request, please make sure that you:
+ * Discussed about it on the discord or the forum,
+ * There is not already a suggestion about it in the issues or in the roadmap: https://trello.com/b/qf0lM7k8/gdevelop-roadmap
+ * Consider commenting on the roadmap if something is important for you
+
+## Description
+Is your feature request **related to a problem**? Please describe.
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+
+## Solution suggested
+**Describe the solution**
+A clear and concise description of what could be done.
+
+Add any other context or screenshots about the feature request here.
+
+Explain if you can help implementing the solution.
+
+## Alternatives considered
+A clear and concise description of any alternative solutions or features you've considered.