Add GitHub Action to label Pull Requests

.github/main.workflow

+workflow "Triage Pull Request" {
+  on = "pull_request"
+  resolves = ["Triage"]
+}
+
+# Only act if there are code changes: if the pull_request
+# event's action is either 'opened' (new PR) or 'synchronize' (new commits)
+action "Filter actions" {
+  uses = "actions/bin/filter@0ac6d44"
+  args = "action 'opened|synchronize'"
+}
+
+action "Triage" {
+  needs = ["Filter actions"]
+  uses = "ohmyzsh/github-actions/pull-request-triage@master"
+  secrets = ["GITHUB_TOKEN"]
+}