chore: use main in CI (#359)

Author: 43081j

.github/workflows/ci.yml

@@ -5,9 +5,9 @@ name: Node.js CI
 
 on:
   push:
-    branches: master
+    branches: main
   pull_request:
-    branches: master
+    branches: main
 
 jobs:
   lint:

README.md

@@ -231,7 +231,7 @@ chai.should();
 // according to your preference of assertion style
 ```
 
-You can of course put this code in a common test fixture file; for an example using [Mocha](http://mochajs.org), see [the Chai as Promised tests themselves](https://github.com/domenic/chai-as-promised/tree/master/test/).
+You can of course put this code in a common test fixture file; for an example using [Mocha](http://mochajs.org), see [the Chai as Promised tests themselves](https://github.com/domenic/chai-as-promised/tree/main/test/).
 
 **Note when using other Chai plugins:** Chai as Promised finds all currently-registered asserters and promisifies them, at the time it is installed. Thus, you should install Chai as Promised _last_, after any other Chai plugins, if you expect their asserters to be promisified.