add beta template (#1561)

.github/ISSUE_TEMPLATE/beta_report.md

@@ -0,0 +1,39 @@
+---
+name: Beta Testing Report
+about: Report issues found while using a beta version of the Mattermost Desktop App
+
+---
+
+I confirm (by marking "x" in the [ ] below: [x]):
+
+- [ ] I have confirmed this is an issue on the newest beta build [available here](https://github.com/mattermost/desktop/tags)
+- [ ] This issue doesn't reproduce on web browsers (such as in Chrome). If it does, [issue reports go to the Mattermost Server repository](https://github.com/mattermost/platform/issues).
+- [ ] I have read [contributing guidelines](https://github.com/mattermost/desktop/blob/master/CONTRIBUTING.md).
+
+---
+
+**Summary**
+<!--
+Issue in one concise sentence.
+-->
+
+**Environment**
+- Operating System:
+- Mattermost Desktop App version: X.X.X <!-- See [Help] > [Version Number] -->
+- Mattermost Server version: X.X.X <!-- See [Mattermost Menu] > [About Mattermost], where [Mattermost Menu] can be accessed by clicking on three dots next to your profile picture -->
+
+**Steps to reproduce**
+
+**Expected behavior**
+
+**Observed behavior**
+
+<!--
+Please include relevant error messages and/or screenshots.
+-->
+
+**Possible fixes**
+
+<!--
+If you can, link to the line of code that might be responsible for the problem.
+-->