(halium) Add ubports/platform-api into manifest

Author: NotKit

snippets/halium.xml

@@ -8,4 +8,5 @@
   </project>
   <project path="vendor/halium/droidmedia" name="Halium/droidmedia" revision="halium-10.0" />
   <project path="vendor/halium/libhybris" name="Halium/libhybris" revision="halium-10.0" />
+  <project path="vendor/halium/platform-api" name="ubports/platform-api" revision="xenial_-_android9" />
 </manifest>