add JDK 17 to CI matrix

Author: SethTisue

.travis.yml

@@ -1,6 +1,5 @@
 version: ~> 1.0 # needed for imports
-
-import: scala/scala-dev:travis/default.yml
+import: SethTisue/scala-dev:travis/default.yml
 
 language: scala
 
@@ -15,6 +14,7 @@ env:
   - ADOPTOPENJDK=8     SCALAJS_VERSION=       CACHE_WORKAROUND=see-PR-335
   - ADOPTOPENJDK=8     SCALAJS_VERSION=1.6.0  CACHE_WORKAROUND=see-PR-335
   - ADOPTOPENJDK=11    SCALAJS_VERSION=       CACHE_WORKAROUND=see-PR-335
+  - ADOPTOPENJDK=17    SCALAJS_VERSION=       CACHE_WORKAROUND=see-PR-335
 
 matrix:
   include: