docs: prepare docs for gumloop addition (apify#1695)

change dosc position to account for  new gumloop documentation
prepare structure for gumloop docs

Author: TC-MO

.github/styles/config/vocabularies/Docs/accept.txt

@@ -83,6 +83,7 @@ preconfigured
 [Zz]apier
 [Tt]rello
 [Pp]refill
+[Gg]umloop
 
 [Mm]ultiselect
 

sources/platform/integrations/workflows-and-notifications/gmail.md

@@ -2,7 +2,7 @@
 title: Gmail integration
 description: Learn how to integrate Apify with Gmail
 sidebar_label: Gmail
-sidebar_position: 5
+sidebar_position: 6
 slug: /integrations/gmail
 ---