Add FileTemplate and FileInfoTemplate documentation for FileSelect and Upload components

[Copilot]

Documents two new templates for FileSelect and Upload components introduced in telerik/blazor#12438:

• FileTemplate: Full customization of file list items, replacing all built-in elements (progress bar, action buttons, file info)
• FileInfoTemplate: Partial customization of file information section while preserving built-in features

Changes

Upload Templates (components/upload/templates.md)

• Added FileTemplate section with FileTemplateContext explanation and example
• Added FileInfoTemplate section with FileInfoTemplateContext explanation and example
• Restructured with table of contents linking to all three templates
• Fixed typo in metadata description

FileSelect Templates (components/fileselect/templates.md)

• Added FileTemplate section with FileTemplateContext explanation and example
• Added FileInfoTemplate section with FileInfoTemplateContext explanation and example
• Restructured with table of contents linking to all three templates
• Removed unnecessary wrapper div from SelectFilesButtonTemplate example

Supporting Changes

• Added FileTemplate and FileInfoTemplate to .spelling dictionary
• Added package-lock.json to .gitignore (was auto-generated during documentation validation)

Example

<TelerikUpload @ref="@UploadRef">
    <FileTemplate Context="fileContext">
        <div style="border: 1px solid gray; padding: 5px; margin: 5px;">
            <strong>File Name:</strong> @fileContext.File.Name <br />
            <strong>Size:</strong> @(fileContext.File.Size / 1024) KB
        </div>
        <TelerikButton OnClick="@(() => { UploadRef.RemoveFileAsync(fileContext.File.Id); })">
            Remove
        </TelerikButton>
    </FileTemplate>
</TelerikUpload>

Original prompt

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This section details on the original issue you should resolve

<issue_title>Documentation for Add file template for the FileSelect and Upload components</issue_title>
<issue_description>Related to: telerik/blazor#12438</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes telerik/blazor#12481

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