fix: corrupted docx issue caused by duplicate extensions in ContentType.xml with different casing

[ACHP]

Description

This PR addresses a bug where the ContentType.xml file could be corrupted due to duplicate entries of the same file extension with different casing. For example, if a template specifies an uppercase extension (JPG), but the generated report inserts a lowercase extension (jpg), the ContentType.xml ends up with two entries:

<Default Extension="JPG" ContentType="image/jpeg"/>
<Default Extension="jpg" ContentType="image/jpeg"/>

As a result, the DOCX file becomes invalid.

Solution

To fix this issue, we updated the ensureContentType function to be case-insensitive when adding new extensions. This change ensures that only one entry is created for a given extension, regardless of its casing.

Changes
• Updated ensureContentType to treat extensions in a case-insensitive manner.

How to reproduce:

• Create a docx file with a JPG image in it, (make sure the extension is uppercase)
• Use it as a templte to insert a jpg (lowercase) image
• open the docx