Update all ExcelJS mentions to DevExtreme ExcelJS (DevExpress#30505)

Author: arman-boyakhchyan

apps/demos/Demos/DataGrid/ExcelJSExportImages/description.md

@@ -1,4 +1,4 @@
-This demo shows how you can use <a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">ExcelJS</a> API to export images to Excel [worksheets](https://github.com/DevExpress/devextreme-exceljs-fork#add-a-worksheet).
+This demo shows how you can use <a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">DevExtreme ExcelJS</a> API to export images to Excel [worksheets](https://github.com/DevExpress/devextreme-exceljs-fork#add-a-worksheet).
 
 See the [customizeCell](/Documentation/ApiReference/Common/Object_Structures/ExportDataGridProps/#customizeCell) callback for implementation details. The **workbook**.<a href="https://github.com/DevExpress/devextreme-exceljs-fork#add-image-to-workbook" target="_blank">addImage()</a> method specifies image data and encoding. **tl** and **br** parameters are used to specify image location and span.
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apps/demos/Demos/DataGrid/ExcelJSHeaderAndFooter/description.md

@@ -1,4 +1,4 @@
-<a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">ExcelJS</a> library allows you to customize worksheets outside the exported cell area. This demo uses this functionality to add a header (a title before exported data) and a footer (a note after exported data).
+<a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">DevExtreme ExcelJS</a> library allows you to customize worksheets outside the exported cell area. This demo uses this functionality to add a header (a title before exported data) and a footer (a note after exported data).
 
 Review the [onExporting](/Documentation/ApiReference/UI_Components/dxDataGrid/Configuration/#onExporting) handler to see the data export code. The functions that create header and footer sections utilize the following customization features:
 

apps/demos/Demos/DataGrid/ExcelJSOverview/description.md

@@ -1,4 +1,4 @@
-To enable export in the DataGrid, reference or import the <a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">ExcelJS</a> and <a href="https://github.com/eligrey/FileSaver.js/" target="_blank">FileSaver</a> libraries. Set **export**.[enabled](/Documentation/ApiReference/UI_Components/dxDataGrid/Configuration/export/#enabled) to **true**. 
+To enable export in the DataGrid, reference or import the <a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">DevExtreme ExcelJS</a> and <a href="https://github.com/eligrey/FileSaver.js/" target="_blank">FileSaver</a> libraries. Set **export**.[enabled](/Documentation/ApiReference/UI_Components/dxDataGrid/Configuration/export/#enabled) to **true**. 
 
 Once the conditions above are met, use the [exportDataGrid(options)](/Documentation/ApiReference/Common/Utils/excelExporter/#exportDataGridoptions) method to export the DataGrid to an Excel <a href="https://github.com/DevExpress/devextreme-exceljs-fork#create-a-workbook" target="_blank">workbook</a>. 
 

apps/demos/Demos/PivotGrid/ExcelJSOverview/description.md

@@ -1,4 +1,4 @@
-Our PivotGrid allows you to easily and accurately export its contents to Microsoft Excel. To enable export operations, you must reference or import <a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">ExcelJS</a> and <a href="https://github.com/eligrey/FileSaver.js/" target="_blank">FileSaver</a> libraries. You must also set **export**.[enabled](/Documentation/ApiReference/UI_Components/dxPivotGrid/Configuration/export/#enabled) to **true**.
+Our PivotGrid allows you to easily and accurately export its contents to Microsoft Excel. To enable export operations, you must reference or import <a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">DevExtreme ExcelJS</a> and <a href="https://github.com/eligrey/FileSaver.js/" target="_blank">FileSaver</a> libraries. You must also set **export**.[enabled](/Documentation/ApiReference/UI_Components/dxPivotGrid/Configuration/export/#enabled) to **true**.
 
 Once you've referenced/imported both files and set **export**.**enabled** to **true**, use the [exportPivotGrid(options)](/Documentation/ApiReference/Common/Utils/excelExporter/#exportPivotGridoptions) method to export PivotGrid content to an Excel <a href="https://github.com/DevExpress/devextreme-exceljs-fork#create-a-workbook" target="_blank">workbook</a>.
 

apps/demos/Demos/PivotGrid/ExcelJsHeaderAndFooter/description.md

@@ -1,4 +1,4 @@
-The PivotGrid allows you to customize a header and a footer in the exported Excel file. The <a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">ExcelJS</a> library allows you to customize worksheets outside of exported cell regions. This, in turns, allows you to add a header (a title before exported data) and a footer (a note after exported data).
+The PivotGrid allows you to customize a header and a footer in the exported Excel file. The <a href="https://github.com/DevExpress/devextreme-exceljs-fork" target="_blank">DevExtreme ExcelJS</a> library allows you to customize worksheets outside of exported cell regions. This, in turns, allows you to add a header (a title before exported data) and a footer (a note after exported data).
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 Follow the steps below to configure a header/footer: