Add unicode arrows, /cc instead of 👀

Author: shawnbot

.github/pull_request_template.md

@@ -1,7 +1,7 @@
----^ First, set the base branch to "dev".
+↖ First, change the base branch from "master" to "dev".
 
-^--- Next, briefly describe your proposal in the title.
+↑ Next, briefly describe your proposal in the title.
 
-Finally, tell us more about the change here.
+Finally, tell us more about the change here, in the description.
 
-:eyes: @primer/ds-core
+/cc @primer/ds-core