Fix link to slack (Broken)

.github/ISSUE_TEMPLATE/feature_request.md

@@ -4,16 +4,16 @@ about: Suggest an idea for this project
 
 ---
 
-For general questions please use [PX4 Discuss](http://discuss.px4.io/) or [Slack](slack.px4.io).
+For general questions please use [PX4 Discuss](http://discuss.px4.io/) or [Slack](http://slack.px4.io/).
 
-**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 [...]
+**Describe problem solved by the proposed feature**
+A clear and concise description of the problem, if any, this feature will solve. E.g. I'm always frustrated when ...
 
-**Describe the solution you'd like**
+**Describe your preferred solution**
 A clear and concise description of what you want to happen.
 
-**Describe alternatives you've considered**
-A clear and concise description of any alternative solutions or features you've considered.
+**Describe possible alternatives**
+A clear and concise description of alternative solutions or features you've considered.
 
 **Additional context**
-Add any other context or screenshots about the feature request here.
+Add any other context or screenshots for the feature request here.