Jpeg filename extension should be recognized as valid thumbnailable format when attaching images to comments. Currently jpg extension is ok, but not jpeg. Both jpg and jpeg should be allowed

This came out of support request: (CSP-10510) Jpeg extension not recognized as a valid jpeg image type for thumbnail creation in comment

Jpeg filename extension should be recognized as valid thumbnailable format when attaching images to comments. Currently jpg extension is ok, but not jpeg. Both jpg and jpeg should be allowed