[fenix] For https://github.com/mozilla-mobile/fenix/issues/5382: Updates bors bot integration with Taskcluster (https://github.com/mozilla-mobile/fenix/pull/5929)

.github/PULL_REQUEST_TEMPLATE

@@ -1,4 +1,5 @@
-
+---
+<!-- Text above this line will be added to the commit once "bors" merges this PR -->
 
 ### Pull Request checklist
 <!-- Before submitting the PR, please address each item -->
@@ -14,4 +15,4 @@
 1. click on Show All Checks,
 2. click Details next to "Taskcluster (pull_request)" after it appears and then finishes with a green checkmark,
 3. click on the "Fenix - assemble" task, then click "Run Artifacts".
-4. the APK links should be on the left side of the screen, named for each CPU architecture
+4. the APK links should be on the left side of the screen, named for each CPU architecture

.taskcluster.yml

@@ -14,18 +14,21 @@ tasks:
           $let:
               # Github events have this stuff in different places...
               ownerEmail:
-                  $if: 'tasks_for == "github-push"'
-                  then: '${event.pusher.email}'
-                  # Assume Pull Request
-                  else:
-                      $if: 'tasks_for == "github-pull-request"'
-                      then: '${event.pull_request.user.login}@users.noreply.github.com'
+                  $if: 'event.sender.login == "bors[bot]"'
+                  then: 'skaspari+mozlando@mozilla.com'   # It must match what's in bors.toml
+                  else: 
+                      $if: 'tasks_for == "github-push"'
+                      then: '${event.pusher.email}'
+                      # Assume Pull Request
                       else:
-                          $if: 'tasks_for == "github-release"'
-                          then: '${event.sender.login}@users.noreply.github.com'
+                          $if: 'tasks_for == "github-pull-request"'
+                          then: '${event.pull_request.user.login}@users.noreply.github.com'
                           else:
-                              $if: 'tasks_for in ["cron", "action"]'
-                              then: '${tasks_for}@noreply.mozilla.org'
+                              $if: 'tasks_for == "github-release"'
+                              then: '${event.sender.login}@users.noreply.github.com'
+                              else:
+                                  $if: 'tasks_for in ["cron", "action"]'
+                                  then: '${tasks_for}@noreply.mozilla.org'
               baseRepoUrl:
                   $if: 'tasks_for in ["github-push", "github-release"]'
                   then: '${event.repository.html_url}'
@@ -88,7 +91,9 @@ tasks:
                   then: ${event.action}
                   else: 'UNDEFINED'
           in:
-              $if: 'tasks_for in ["github-pull-request", "action", "cron"] || (tasks_for == "github-push" && head_branch[:10] != "refs/tags/") || (tasks_for == "github-release" && releaseAction == "published")'
+              $if: 'tasks_for in ["github-pull-request", "action", "cron"] 
+              || (tasks_for == "github-push" && head_branch[:10] != "refs/tags/") && (head_branch != "staging.tmp") && (head_branch != "trying.tmp")
+              || (tasks_for == "github-release" && releaseAction == "published")'
               then:
                   $let:
                       level: