github issues: add support button

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,6 @@
+blank_issues_enabled: false
+contact_links:
+    - name: Support
+      url: https://stackoverflow.com/questions/tagged/mitmproxy
+      about: Please do not use GitHub for support requests.
+             If you have questions on how to use mitmproxy, please ask them on StackOverflow!

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,5 +1,5 @@
 ---
-name: Feature request
+name: Proposal
 about: Suggest an idea for this project
 title: ''
 labels: kind/feature
@@ -7,14 +7,15 @@ assignees: ''
 
 ---
 
-#### 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 [...]
+#### Problem Description
 
-#### Describe the solution you'd like
+A clear and concise description of the problem you are trying to solve.
+
+#### Proposal
 A clear and concise description of what you want to happen.
 
-#### Describe alternatives you've considered
+#### Alternatives
 A clear and concise description of any 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 about the proposal here.