chore(): change branch from master to main accross the codebase (decaporg#7154)

Author: demshy

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,7 +2,7 @@
 Thanks for submitting a pull request!
 
 Please make sure you've read and understood our contributing guidelines here:
-https://github.com/decaporg/decap-cms/blob/master/CONTRIBUTING.md
+https://github.com/decaporg/decap-cms/blob/main/CONTRIBUTING.md
 
 If this is a bug fix, make sure your description includes "fixes #xxxx", or
 "closes #xxxx", where #xxxx is the issue number.
@@ -29,6 +29,6 @@ Example: The exact commands you ran and their output, screenshots / videos if th
 
 Please add a `x` inside each checkbox:
 
-- [ ] I have read the [contribution guidelines](https://github.com/decaporg/decap-cms/blob/master/CONTRIBUTING.md).
+- [ ] I have read the [contribution guidelines](https://github.com/decaporg/decap-cms/blob/main/CONTRIBUTING.md).
 
 **A picture of a cute animal (not mandatory but encouraged)**

.github/workflows/nodejs.yml

@@ -3,7 +3,7 @@ name: Node CI
 on:
   push:
     branches:
-      - master
+      - main
   pull_request:
     types: [opened, synchronize, reopened]