Add header to device port issue template

As suggested by @z3ntu this adds a header to the issue template. This makes it
possible to select the issue template when opening a new issue.

ISSUE_TEMPLATE/device-port.md → .github/ISSUE_TEMPLATE/device-port.md

@@ -1,3 +1,8 @@
+---
+name: Device port
+about: Template for tracking progress of device ports
+---
+
 Tree: <!-- halium-5.1 or halium-7.1 -->
 
 - [ ] Create manifest <!-- Link to the manifest, contained in a pull request to https://github.com/Halium/halium-devices -->
@@ -21,4 +26,4 @@ Tree: <!-- halium-5.1 or halium-7.1 -->
 Other information goes below this comment. Possible topics of comment may 
 include special flashing or building instructions, such as manual effort to
 change vendor files.
--->
+-->