Add workflow to publish gem on tag. (#285)

.github/workflows/publish.yml

@@ -0,0 +1,28 @@
+name: Ruby Gem
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  build:
+    name: Build + Publish
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-ruby@v1
+      with:
+        ruby-version: 2.7.x
+
+    - name: Publish to RubyGems
+      run: |
+        mkdir -p $HOME/.gem
+        touch $HOME/.gem/credentials
+        chmod 0600 $HOME/.gem/credentials
+        printf -- "---\n:rubygems_api_key: ${GEM_HOST_API_KEY}\n" > $HOME/.gem/credentials
+        gem build droplet_kit.gemspec
+        gem push *.gem
+      env:
+        GEM_HOST_API_KEY: "${{secrets.RUBYGEMS_AUTH_TOKEN}}"

RELEASE.md

@@ -3,20 +3,17 @@
 Once the changes have been merged to main it's time to release a new
 version of the gem.
 
-1. Creating a PR with a semantic version
-bump to
+1. Creating a PR with a semantic version bump to
 [version](https://github.com/digitalocean/droplet_kit/blob/main/lib/droplet_kit/version.rb)
 and all the changes being released added to the
 [CHANGELOG](https://github.com/digitalocean/droplet_kit/blob/main/CHANGELOG.md).
-1. After the PR has been merged, create a release
-on github for the new version:
-    - The tag should be in the format of: vX.Y.Z 
+1. After the PR has been merged, create a release on GitHub for the new version:
+    - The tag should be in the format of: vX.Y.Z
         - You can think of X.Y.Z as such:
             X = breaking
             Y = feature
             Z = bugfix
     - The title should be in the format of: vX.Y.Z (same as tag)
     - The description should include all the changes being released in the format of:
         - #[PR #] - @[contributor] - [description]
-1. The release will be pushed to rubygems by a concourse job. Concourse checks the
-repo for a new release every 5 minutes, so there's a slight delay.
+1. When the tag is created, a GitHub Actions workflow will publish the release to rubygems.