docs: change master to main (#6995)

Author: martinjagodic

website/content/docs/add-to-your-site.md

@@ -95,7 +95,7 @@ For GitHub and GitLab repositories, you can start your Decap CMS `config.yml` fi
 ```yaml
 backend:
   name: git-gateway
-  branch: master # Branch to update (optional; defaults to master)
+  branch: main # Branch to update (optional; defaults to master)
 ```
 
 *(For Bitbucket repositories, use the [Bitbucket backend](/docs/bitbucket-backend) instructions instead.)*

website/content/docs/gitea-backend.md

@@ -23,7 +23,7 @@ backend:
   api_root: https://gitea.example.com/api/v1 # API URL of your Gitea instance
   base_url: https://gitea.example.com # Root URL of your Gitea instance
   # optional, defaults to master
-  # branch: master
+  # branch: main
 ```
 
 ## Git Large File Storage (LFS)