re-add pg core component to avoid braking legacy applications

Author: pascalwengerter

app/concepts/pg/cell/pg.rb

@@ -0,0 +1,5 @@
+module Pg::Cell
+  class Pg < Component::Cell::Static
+
+  end
+end

app/concepts/pg/view/pg.haml

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+- if options[:text].nil?
+  %p{@tag_attributes}
+    - if block_given?
+      = yield
+
+- else
+  %p{@tag_attributes}
+    = options[:text]

docs/components/pg.md

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+# matestack core component: PG
+
+Show [specs](../../spec/usage/components/pg_spec.rb)
+
+The HTML `<p>` tag implemented in ruby. Please refer to the [paragraph core component](./paragraph.md) since the PG component is deprecated and will be removed sometime in the future.

spec/usage/components/pg_spec.rb

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+require_relative '../../support/utils'
+include Utils
+
+describe 'Paragraph Component', type: :feature, js: true do
+
+  it 'Example 1' do
+
+    class ExamplePage < Page::Cell::Page
+
+      def response
+        components {
+          # simple paragraph
+          pg text: 'I am simple'
+
+          # enhanced paragraph
+          pg id: 'my-id', class: 'my-class' do
+            plain 'I am enhanced'
+          end
+        }
+      end
+
+    end
+
+    visit '/example'
+
+    static_output = page.html
+
+    expected_static_output = <<~HTML
+    <p>I am simple</p>
+    <p id="my-id" class="my-class">I am enhanced</p>
+    HTML
+
+    expect(stripped(static_output)).to include(stripped(expected_static_output))
+  end
+
+end