[feature] Add customizable commit message

[build] Add `@zeit/ncc` dev package and basic build command
[readme] Update README with action input descriptions

README.md

@@ -13,9 +13,32 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: everlytic/branch-merge@1.0.2
+      - uses: everlytic/branch-merge@1.1.0
         with:
           github_token: ${{ github.token }}
           source_ref: ${{ github.ref }}
           target_branch: 'master'
+          commit_message_template: '[Automated] Merged {source_ref} into target {target_branch}'
 ```
+
+## Inputs
+
+### `github_token`
+**Required** - The GitHub Personal Access Token used to perform the merge action. 
+This can be the [Token provided by GitHub Workflows](https://docs.github.com/en/actions/configuring-and-managing-workflows/authenticating-with-the-github_token), 
+or a custom token set at a [workflow secret](https://docs.github.com/en/actions/configuring-and-managing-workflows/creating-and-storing-encrypted-secrets).
+
+A custom token may be useful if performing actions that require Administrative privileges, such as overriding 
+branch protection rules.
+
+### `source_ref`
+**Required** - The source ref or branch name that you wish to merge into the `target_branch`.
+
+### `target_branch`
+**Required** - The target branch you are merging into.
+
+### `commit_message_template`
+**Optional** - Customize the commit message that gets added to the merge commit. This allows for templates enclosed in 
+curly braces `{}`. 
+
+The only templates allowed at this time are `{source_ref}` and `{target_branch}`.

action.yml

@@ -2,16 +2,20 @@ name: 'Branch Merge'
 description: 'Merges a source branch, or SHA1 ref into a target branch'
 inputs:
   github_token:
-    description: 'Token to authenticate with GitHub'
+    description: 'Token used to authenticate with GitHub when performing the merge command.'
     required: true
     default: ${{ github.token }}
   source_ref:
-    description: 'Branch or SHA1 ref that you are merging into the target_branch.'
+    description: 'Branch name or Ref that you wish to merge into the target_branch.'
     required: true
     default: ${{ github.ref }}
   target_branch:
-    description: 'Branch you are merging into'
+    description: 'Branch you are merging the source ref into.'
     required: true
+  commit_message_template:
+    description: 'Template to generate the commit message, see README.md for more info'
+    required: false
+    default: 'Merged {source_ref} into {target_branch}.'
 runs:
   using: 'node12'
   main: 'dist/index.js'