Ignore extension when deduplicating option

[matthewkeller36]

Implements duplication checking while ignoring file extensions. Addresses feature request I had mentioned in #191. Uses a.Type to add an extra layer of security when determining if files are duplicates. Feature can be invoked using -ignore-extension in the command line

[matthewkeller36]

One issue I am seeing with using strings.TrimSuffix is the OriginalFileName already contains the extension and the duplicateKey is appending a second extension. Example:
a.OriginalFileName: IMG_0394.HEIC
a.OriginalFileName + path.Ext(a.OriginalPath): IMG_0394.HEIC.HEIC

This was why I was originally using strings.Cut as TrimSuffix will only remove one of the extensions. I believe this issue could be avoided by not appending path.Ext(a.OriginalPath) to the duplicateKey.