Bug 1572316 - Add l10n-bumper-beta task. r=darktrojan

This is distinct from the default task because "dontbuild" is "false"
(or run a build). This job will run on merge day after the
central-to-beta merge. It will also run on comm-beta after updating
.gecko_rev.yml, which generally is one of the first things done when
preparing a new Thunderbird release.

--HG--
extra : rebase_source : d8aa3258539cddf0540dbdb10d3170d90387a793
extra : histedit_source : 5457188a41d9e540995297b1d810b73274b2737b

taskcluster/ci/l10n-bump/kind.yml

@@ -85,3 +85,19 @@ jobs:
             platform: linux64/opt
             symbol: l10n-bump(lb)
             tier: 1
+    l10n-bumper-beta:
+        name: l10n_bumper_beta
+        description: l10n changesets bumper (beta merges)
+        run-on-projects: ['comm-beta']
+        worker:
+            dontbuild: false
+            ignore-closed-tree: true
+        treeherder:
+            kind: build
+            platform: linux64/opt
+            symbol: l10n-bump(lb-beta)
+            tier: 1
+        optimization:
+            skip-unless-changed:
+                - mail/config/version.txt
+                - .gecko_rev.yml