3356592-readme-add.

Closes #3356592

README.md

+CONTENTS OF THIS FILE
+---------------------
+
+ * Introduction to Viewer
+ * Requirement
+ * Installation
+ * Maintainers
+
+
+# Introduction to Viewer
+
+* The Viewer module is a simple and yet powerful module to import and process
+ structured or unstructured file types such as CSV, XLSX/XLS, PDF and present
+ them in Drupal via Viewer reference field or a Block.
+* This module comes with multiple plugin support for various data. Some of the
+ plugins include integration with Chart.js, ApexCharts, Datatables, and etc.
+* The user may easily organize your data and display each file in a tab
+ (horizontal or vertical), accordions and other options could be also added.
+* This module can import files from different locations it could be FTP, SFTP,
+ absolute path, remote URL or manual upload.
+* Automated imports on cron are also supported.
+* The module could be useful to show financial information, analytical data or
+ any other files on your site.
+
+* For a full description of the module, visit the
+[project page](https://www.drupal.org/project/viewer).
+
+* Submit bug reports and feature suggestions, or track changes in the
+[issue queue](https://www.drupal.org/project/issues/viewer).
+
+
+## Requirements
+
+This module requires no modules outside of Drupal core.
+
+
+## Installation
+
+Install as you would normally install a contributed Drupal module. For further
+information, see
+[Installing Drupal Modules](https://www.drupal.org/docs/extending-drupal/installing-drupal-modules).
+
+## Basic use
+
+1. Create a Source at /admin/structure/viewer-source. This can a PDF, CSV or XLSX file referenced from a URL or path, or loaded via S/FTP or file upload.
+2. Create one or more Viewers from this source at /admin/structure/viewers. This Viewer can render the source as a table or chart, with descriptive text fields such as a title, subtitle or summary.
+3. The Viewer can be embedded into the site:
+    1. As a Viewer block (via /admin/structure/block).
+    2. Referenced through a custom field in a content type (add a General > Viewer field to the Content type).
+    3. Inserted by CKEditor in Long Text fields. Edit or create a new text format at /admin/config/content/formats:
+        * Select CKEditor 5 as the Text Editor
+        * Add the Viewer button to the CKEditor toolbar
+        * Enable the Viewer filter 
+
+## MAINTAINERS
+
+Current maintainers:
+
+* Minnur Yunusov (https://www.drupal.org/u/minnur)