Update default branch reference from master to main (#79)

Signed-off-by: Carlos Panato <[email protected]>

README.md

@@ -30,7 +30,7 @@ name: Release Charts
 on:
   push:
     branches:
-      - master
+      - main
 
 jobs:
   release:
@@ -58,7 +58,7 @@ jobs:
 ```
 
 This uses [@helm/chart-releaser-action](https://www.github.com/helm/chart-releaser-action) to turn your GitHub project into a self-hosted Helm chart repo.
-It does this – during every push to `master` – by checking each chart in your project, and whenever there's a new chart version, creates a corresponding [GitHub release](https://help.github.com/en/github/administering-a-repository/about-releases) named for the chart version, adds Helm chart artifacts to the release, and creates or updates an `index.yaml` file with metadata about those releases, which is then hosted on GitHub Pages
+It does this – during every push to `main` – by checking each chart in your project, and whenever there's a new chart version, creates a corresponding [GitHub release](https://help.github.com/en/github/administering-a-repository/about-releases) named for the chart version, adds Helm chart artifacts to the release, and creates or updates an `index.yaml` file with metadata about those releases, which is then hosted on GitHub Pages
 
 ## Code of conduct