Update the 3.x branch (#229)

* Update issue templates

* Update UPGRADE.md

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,41 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: "[Bug]"
+labels: bug
+assignees: ''
+
+---
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Go to '...'
+2. Click on '....'
+3. Scroll down to '....'
+4. See error
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+If applicable, add screenshots to help explain your problem.
+
+**Logs**
+If applicable, add the verbose output of `flutter run`.
+
+**Environment (please complete the following information):**
+ - [ ] iOS? Version: ...
+ - [ ] Android? Version: ...
+ - [ ] Real Device? Which?: ...
+ - [ ] Emulator/Simulator? Which?: ...
+ - Version of `barcode_scan`
+ - Output of `flutter --version`:
+```
+Flutter ...
+```
+
+**Additional context**
+Add any other context about the problem here.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,20 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: "[Feature Request]"
+labels: Feature
+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 [...]
+
+**Describe the solution you'd like**
+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.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.

UPGRADE.md

@@ -4,6 +4,8 @@ The `BarcodeScan.scan()` method returns a [`ScanResult`](./lib/model/scan_result
 The barcode is stored in `ScanResult.rawContent`
 Check your calls to this method and read the barcode from the `rawContent` property.
 
+If your project uses pre Flutter 1.12 you need to update Flutter in your App: https://github.com/flutter/flutter/wiki/Upgrading-pre-1.12-Android-projects
+
 
 # Upgrade from 1.0.0 to 2.0.0