Add new e2e test for adding and editing comments

...on issues.

qa/qa/specs/features/browser_ui/2_plan/issue/comment_issue_spec.rb

+# frozen_string_literal: true
+
+module QA
+  context 'Plan' do
+    describe 'Issue comments' do
+      it 'user comments on an issue and edits the comment' do
+        Runtime::Browser.visit(:gitlab, Page::Main::Login)
+        Page::Main::Login.act { sign_in_using_credentials }
+
+        issue = Resource::Issue.fabricate_via_api! do |issue|
+          issue.title = 'issue title'
+        end
+        issue.visit!
+
+        Page::Project::Issue::Show.perform do |issue_show_page|
+          first_version_of_comment = 'First version of the comment'
+          second_version_of_comment = 'Second version of the comment'
+
+          issue_show_page.comment(first_version_of_comment)
+
+          expect(issue_show_page).to have_content(first_version_of_comment)
+
+          issue_show_page.edit_comment(second_version_of_comment)
+
+          expect(issue_show_page).to have_content(second_version_of_comment)
+          expect(issue_show_page).not_to have_content(first_version_of_comment)
+        end
+      end
+    end
+  end
+end