more stuff we care about

Signed-off-by: Miek Gieben <miek@miek.nl>

.github/pull_request_template.md

@@ -1,6 +1,9 @@
-Note that dependencies version bumps PRs will be closed.
+Note that dependencies version bumps PRs will not be merged. Downstream projects manage their
+dependencies by themselves, what we do here doesn't matter. See
+https://github.com/miekg/dns/pull/1049#issuecomment-565718842 and
+https://github.com/golang/go/issues/35798#issuecomment-558358674 for more context.
 
-Downstream projects manage their dependencies by themselves, what we do here doesn't matter.
+If your PR introduces backward incompatible changes it will very likely not be merged.
 
-See https://github.com/miekg/dns/pull/1049#issuecomment-565718842 and
-https://github.com/golang/go/issues/35798#issuecomment-558358674 for more context.
+We support the last two major Go versions, if your PRs uses features from a too new Go version, it
+will not be merged.