Add more files to the buildpack publishing file exclusion list (#1637)

Since these files aren't needed for the buildpack to run,
so can be excluded from the archive published to the
buildpack registry.

Author: edmorley

buildpack.toml

@@ -5,9 +5,11 @@ name = "Python"
 files = [
   ".github/",
   "builds/",
+  "etc/publish.sh",
   "spec/",
   ".gitignore",
   ".rubocop.yml",
+  ".shellcheckrc",
   "Gemfile",
   "Gemfile.lock",
   "hatchet.json",