Add triggers for 'main' branch (#29505)

- part of #29475

Author: dougbu

.azure/pipelines/ci.yml

@@ -8,6 +8,7 @@ trigger:
   branches:
     include:
     - master
+    - main
     - release/*
     - internal/release/*
 

.azure/pipelines/helix-matrix.yml

@@ -7,6 +7,7 @@ schedules:
   branches:
     include:
     - master
+    - main
   always: true
 - cron: "0 9 * * *"
   branches:

.azure/pipelines/quarantined-pr.yml

@@ -9,6 +9,7 @@ trigger:
   branches:
     include:
     - master
+    - main
     - release/5.0
 
 # Run PR validation on branches that include Helix tests
@@ -17,6 +18,7 @@ pr:
   branches:
     include:
     - master
+    - main
     - release/5.0
   paths:
     exclude:
@@ -36,6 +38,7 @@ schedules:
   branches:
     include:
     - master
+    - main
   always: true
 
 variables: