Sync notifications and troubleshooting guides (#998)

* Add help articles

* Broadcast sync messages as notifications

* Lint fixes

* more lint fixes

* Remove redundant code

app/models/help/article.rb

@@ -0,0 +1,54 @@
+class Help::Article
+  attr_reader :frontmatter, :content
+
+  def initialize(frontmatter:, content:)
+    @frontmatter = frontmatter
+    @content = content
+  end
+
+  def title
+    frontmatter["title"]
+  end
+
+  def html
+    render_markdown(content)
+  end
+
+  class << self
+    def root_path
+      Rails.root.join("docs", "help")
+    end
+
+    def find(slug)
+      Dir.glob(File.join(root_path, "*.md")).each do |file_path|
+        file_content = File.read(file_path)
+        frontmatter, markdown_content = parse_frontmatter(file_content)
+
+        return new(frontmatter:, content: markdown_content) if frontmatter["slug"] == slug
+      end
+
+      nil
+    end
+
+    private
+
+      def parse_frontmatter(content)
+        if content =~ /\A---(.+?)---/m
+          frontmatter = YAML.safe_load($1)
+          markdown_content = content[($~.end(0))..-1].strip
+        else
+          frontmatter = {}
+          markdown_content = content
+        end
+
+        [ frontmatter, markdown_content ]
+      end
+  end
+
+  private
+
+    def render_markdown(content)
+      markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML)
+      markdown.render(content)
+    end
+end