Move documentation to a Jekyll site

.gitignore

@@ -1,2 +1,3 @@
 node_modules/
 package-lock.json
+.vscode/

docs/.gitignore

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+_site
+.sass-cache
+.jekyll-cache
+.jekyll-metadata
+vendor
+Gemfile.lock

docs/404.md

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+---
+permalink: /404.html
+nav_exclude: true
+---
+
+# 404
+
+The requested page could not be found.

docs/Gemfile

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+source "https://rubygems.org"
+
+gem "just-the-docs"
+gem "jekyll", "~> 4", group: :jekyll_plugins
+
+group :jekyll_plugins do
+  gem "jekyll-default-layout"
+  gem "jekyll-seo-tag"
+  gem "jekyll-sitemap"
+end

docs/_config.yml

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+title: PR Preview Action
+tagline: A GitHub Action for previewing pull requests
+description: >-
+  Documentation for PR Preview Action, a GitHub Action that deploys pull
+  request previews to GitHub Pages (and removes them after merge).
+baseurl: ""
+url: https://rossjrw.com/
+
+permalink: pretty
+
+author:
+  url: https://rossjrw.com/
+
+theme: just-the-docs
+
+aux_links:
+  GitHub:
+    - "https://github.com/rossjrw/pr-preview-action"
+
+gh_edit_link: true
+gh_edit_link_text: Edit this page on GitHub
+gh_edit_repository: https://github.com/rossjrw/pr-preview-action
+gh_edit_branch: main
+gh_edit_source: docs
+
+ga_tracking: G-19V908BQMY
+
+plugins:
+  - jekyll-seo-tag

docs/index.md

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+---
+layout: home
+---