CI: Add docs pipeline for main pipelines (#45740)

* Add docs pipeline for main

* Extract trigger docs

* Change trigger for main

scripts/drone/pipelines/docs.star

@@ -23,9 +23,8 @@ load(
     'pipeline',
 )
 
-ver_mode = 'pr'
 
-def docs_pipelines(edition):
+def docs_pipelines(edition, ver_mode, trigger):
     steps = [download_grabpl_step()] + initialize_step(edition, platform='linux', ver_mode=ver_mode)
 
     # Insert remaining steps
@@ -34,8 +33,14 @@ def docs_pipelines(edition):
         build_docs_website_step(),
     ])
 
-    trigger = {
-        'event':  [
+    return pipeline(
+        name='{}-docs'.format(ver_mode), edition=edition, trigger=trigger, services=[], steps=steps,
+    )
+
+
+def trigger_docs():
+    return {
+        'event': [
             'pull_request',
         ],
         'paths': {
@@ -45,8 +50,3 @@ def docs_pipelines(edition):
             ],
         },
     }
-    return [
-        pipeline(
-            name='pr-docs', edition=edition, trigger=trigger, services=[], steps=steps,
-        ),
-    ]