Update readme

.gitignore

@@ -1 +1,3 @@
-/.idea/
+.idea/
+*.iml
+.DS_Store

README.adoc

@@ -0,0 +1,125 @@
+= JReleaser
+:linkattrs:
+:project-owner:   jreleaser
+:project-name:    github-action
+
+image:https://github.com/{project-owner}/{project-name}/workflows/Test/badge.svg["Build Status", link="https://github.com/{project-owner}/{project-name}/actions"]
+image:https://img.shields.io/github/v/release/{project-owner}/{project-name}[GitHub release]
+image:https://img.shields.io/twitter/follow/{project-owner}?style=social[Twitter Follow]
+
+This action executes a link:https://jreleaser.org[JReleaser] workflow.
+
+== Usage
+
+=== Workflow
+
+[source,yaml]
+----
+name: release
+
+on:
+  workflow_dispatch:
+
+jobs:
+  release:
+    name: Release
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2.3.4
+
+      # Configure build steps as you'd normally do
+
+      - name: Setup Java
+        uses: actions/setup-java@v1.4.3
+        with:
+          java-version: 1.8
+          server-id: central
+          server-username: MAVEN_USERNAME
+          server-password: MAVEN_CENTRAL_TOKEN
+          gpg-private-key: ${{ secrets.GPG_PRIVATE_KEY }}
+          gpg-passphrase: MAVEN_GPG_PASSPHRASE
+
+      # Post JARs to Maven Central
+
+      - name: Release to Maven Central
+        env:
+          MAVEN_USERNAME: ${{ secrets.SONATYPE_USERNAME }}
+          MAVEN_CENTRAL_TOKEN: ${{ secrets.SONATYPE_PASSWORD }}
+          MAVEN_GPG_PASSPHRASE: ${{ secrets.GPG_PASSPHRASE }}
+        run: |
+          export GPG_TTY=$(tty)
+          git config user.name "${{ github.event.head_commit.committer.name }}"
+          git config user.email "${{ github.event.head_commit.committer.email }}"
+          mvn -B --file pom.xml release:prepare release:perform
+
+      # Create a release
+
+      - name: Run JReleaser
+        uses: jreleaser/github-action@v1
+        env:
+          JRELEASER_GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+----
+
+The last step executes a `full-release` with the default `jreleaser.yml` configuration that's expected
+to be located at the root of the repository.
+
+== Customizing
+
+== Inputs
+
+Following inputs can be used as `step.with` keys
+
+[%header]
+|===
+| Name      | Type   | Default      | Description
+| version   | String | early-access | The JReleaser version to use. Should match any of the
+link:https://github.com/jreleaser/jreleaser/releases[published releases].
+| arguments | String | full-release | The JReleaser command to run.
+|===
+
+== Environment Variables
+
+Following environment variables can be used as `step.env` keys
+
+[%header]
+|===
+| Name                   | Description
+| JRELEASER_GITHUB_TOKEN | link:https://help.github.com/en/actions/configuring-and-managing-workflows/authenticating-with-the-github_token[GITHUB_TOKEN]
+as provided by `secrets`
+|===
+
+== Caution
+
+The default `GITHUB_TOKEN` from `secrets` is link:https://help.github.com/en/actions/configuring-and-managing-workflows/authenticating-with-the-github_token#about-the-github_token-secret[limited]
+to the repository that contains your worklow.
+
+Pushing to other repositories such as Homebrew tap requires additional permissions, you must create a custom
+link:https://help.github.com/articles/creating-a-personal-access-token-for-the-command-line/[Personal Access Token] with
+`repo` permissions and link:https://help.github.com/en/actions/automating-your-workflow-with-github-actions/creating-and-using-encrypted-secrets[add it as a secret in the repository].
+If you create a secret named `GH_PAT`, the step will look like this
+
+[source,yaml]
+----
+      - name: Run JReleaser
+        uses: jreleaser/github-action@v1
+        env:
+          JRELEASER_GITHUB_TOKEN: ${{ secrets.GH_PAT }}
+----
+
+If you'd rather have separate tokens for each additional repository and keep the original `GITHUB_TOKEN` intact then
+you may apply the `GH_PAT` token as follows
+
+[source,yaml]
+----
+      - name: Run JReleaser
+        uses: jreleaser/github-action@v1
+        env:
+          JRELEASER_GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          JRELEASER_HOMEBREW_GITHUB_TOKEN: ${{ secrets.GH_PAT }}
+----
+
+Additional environment variables may be needed depending on your specific setup. Review the docs at
+link:https://jreleaser.org[].
+